diff --git a/src/mathed/formula.C b/src/mathed/formula.C
index 01c3f227e3..9dc7b582c3 100644
--- a/src/mathed/formula.C
+++ b/src/mathed/formula.C
@@ -61,24 +61,13 @@ using std::getline;
 
 
 InsetFormula::InsetFormula()
-	: par_(MathAtom(new MathHullInset))
-{
-	init();
-}
-
-
-InsetFormula::InsetFormula(InsetFormula const & f)
-	: InsetFormulaBase(f), par_(f.par_), loader_(f.loader_.filename())
-{
-	init();
-}
+	: par_(MathAtom(new MathHullInset)), loader_(0)
+{}
 
 
 InsetFormula::InsetFormula(MathInsetTypes t)
-	: par_(MathAtom(new MathHullInset(t)))
-{
-	init();
-}
+	: par_(MathAtom(new MathHullInset(t))), loader_(0)
+{}
 
 
 InsetFormula::InsetFormula(string const & s)
@@ -94,8 +83,8 @@ InsetFormula::InsetFormula(string const & s)
 			par_ = MathAtom(new MathHullInset(LM_OT_SIMPLE));
 		}
 	}
-	init();
 	metrics();
+	updatePreview();
 }
 
 
@@ -167,6 +156,7 @@ void InsetFormula::read(Buffer const *, LyXLex & lex)
 {
 	mathed_parse_normal(par_, lex);
 	metrics();
+	updatePreview();
 }
 
 
@@ -189,7 +179,7 @@ void InsetFormula::draw(BufferView * bv, LyXFont const & font,
 	MathPainterInfo pi(bv->painter());
 
 	if (canPreview()) {
-		pi.pain.image(x + 1, y - a + 1, w - 2, h - 2, *(loader_.image()));
+		pi.pain.image(x + 1, y - a + 1, w - 2, h - 2, *(loader_->image()));
 	} else {
 		pi.base.style = display() ? LM_ST_DISPLAY : LM_ST_TEXT;
 		pi.base.font  = font;
@@ -354,6 +344,8 @@ InsetFormula::localDispatch(BufferView * bv, kb_action action,
 			result = InsetFormulaBase::localDispatch(bv, action, arg);
 	}
 
+	//updatePreview();
+
 	return result;
 }
 
@@ -404,7 +396,7 @@ int InsetFormula::ascent(BufferView *, LyXFont const &) const
 	const int a = par_->ascent();
 	if (!canPreview())
 		return a + 1;
-	return a + 1 - (par_->height() - loader_.image()->getHeight()) / 2;
+	return a + 1 - (par_->height() - loader_->image()->getHeight()) / 2;
 }
 
 
@@ -413,14 +405,14 @@ int InsetFormula::descent(BufferView *, LyXFont const &) const
 	const int d = par_->descent();
 	if (!canPreview())
 		return d + 1;
-	return d + 1 - (par_->height() - loader_.image()->getHeight()) / 2;
+	return d + 1 - (par_->height() - loader_->image()->getHeight()) / 2;
 }
 
 
 int InsetFormula::width(BufferView * bv, LyXFont const & font) const
 {
 	metrics(bv, font);
-	return canPreview() ? loader_.image()->getWidth() : par_->width();
+	return canPreview() ? loader_->image()->getWidth() : par_->width();
 }
 
 
@@ -436,85 +428,78 @@ MathInsetTypes InsetFormula::getType() const
 
 bool InsetFormula::canPreview() const
 {
-	return lyxrc.preview && !par_->asNestInset()->editing()
-		&& loader_.status() == grfx::Ready;
+	return lyxrc.preview && loader_ && !par_->asNestInset()->editing()
+		&& loader_->status() == grfx::Ready;
 }
 
 
 void InsetFormula::statusChanged()
 {
-	//lyxerr << "### InsetFormula::statusChanged called!, status: "
-	//	<< loader_.status() << "\n";
-	if (loader_.status() == grfx::Ready) 
+	lyxerr << "### InsetFormula::statusChanged called!, status: "
+		<< loader_->status() << "\n";
+	if (loader_->status() == grfx::Ready) 
 		view()->updateInset(this, false);
-	else if (loader_.status() == grfx::WaitingToLoad)
-		loader_.startLoading();
+	else if (loader_->status() == grfx::WaitingToLoad)
+		loader_->startLoading();
 }
 
 
-void InsetFormula::init()
-{
-	if (lyxrc.preview)
-		loader_.statusChanged.connect
-			(boost::bind(&InsetFormula::statusChanged, this));
-}
-
-
-// built some unique filename
-string constructFileName(string const & data)
-{
-	typedef std::map<string, int> cache_type;
-	static cache_type theCache;
-	static int theCounter = 0;
-
-	int number;
-	cache_type::const_iterator it = theCache.find(data);
-	if (it == theCache.end()) 
-		number = theCache[data] = theCounter++;
-	else
-		number = it->second;
-	
-	ostringstream os;
-	os << number;
-	return os.str();
-}
-
-
-void InsetFormula::updatePreview() const
+void InsetFormula::updatePreview()
 {
 	// nothing to be done if no preview requested
+	lyxerr << "### updatePreview() called\n";
 	if (!lyxrc.preview)
 		return;
-	//lyxerr << "### updatePreview() called\n";
 
 	// get LaTeX 
 	ostringstream ls;
 	WriteStream wi(ls, false, false);
 	par_->write(wi);
 	string const data = ls.str();
-	string const base = constructFileName(data);
-	string const dir  = OnlyPath(lyx::tempName());
-	string const file = dir + base + ".lyxpreview";
 
-	// everything is fine already
-	if (loader_.filename() == file)
+	// the preview cache, maps contents to image loaders
+	typedef std::map<string, boost::shared_ptr<grfx::Loader> > cache_type;
+	static cache_type theCache;
+	static int theCounter = 0;
+
+	// set our loader corresponding to our current data
+	cache_type::const_iterator it = theCache.find(data);
+
+	// is this old data?
+	if (it != theCache.end()) {
+		// we have already a loader, connect to it anyway
+		lyxerr << "### updatePreview(), old loader: " << loader_ << "\n";
+		loader_ = it->second.get();
+		loader_->statusChanged.connect
+			(boost::bind(&InsetFormula::statusChanged, this));
 		return;
+	}
+
+	// construct new file name
+	static string const dir = OnlyPath(lyx::tempName());
+	ostringstream os;
+	os << dir << theCounter++ << ".lyxpreview";
+	string file = os.str();
 
 	// the real work starts
-	//lyxerr << "### updatePreview() called for " << file << "\n";
+	lyxerr << "### updatePreview(), new file " << file << "\n";
 	std::ofstream of(file.c_str());
 	of << "\\batchmode"
-	   << "\\documentclass{article}"
-	   << "\\usepackage{amssymb}"
-	   << "\\thispagestyle{empty}"
-	   << "\\pdfoutput=0"
-	   << "\\begin{document}"
-	   << data
-	   << "\\end{document}\n";
+		 << "\\documentclass{article}"
+		 << "\\usepackage{amssymb}"
+		 << "\\thispagestyle{empty}"
+		 << "\\pdfoutput=0"
+		 << "\\begin{document}"
+		 << data
+		 << "\\end{document}\n";
 	of.close();
 
 	// now we are done, start actual loading we will get called back via
 	// InsetFormula::statusChanged() if this is finished
-	loader_.reset(file);
+	lyxerr << "### updatePreview(), new loader: " << loader_ << "\n";
+	theCache[data].reset(new grfx::Loader(file));
+	loader_ = theCache.find(data)->second.get();
+	loader_->startLoading();
+	loader_->statusChanged.connect(boost::bind(&InsetFormula::statusChanged, this));
 }
 
diff --git a/src/mathed/formula.h b/src/mathed/formula.h
index 12e94a5203..7ee57310c2 100644
--- a/src/mathed/formula.h
+++ b/src/mathed/formula.h
@@ -39,8 +39,6 @@ public:
 	///
 	explicit InsetFormula(string const &);
 	///
-	InsetFormula(InsetFormula const &);
-	///
 	int ascent(BufferView *, LyXFont const &) const;
 	///
 	int descent(BufferView *, LyXFont const &) const;
@@ -95,15 +93,13 @@ private:
 	///
 	void statusChanged();
 	///
-	void init();
-	///
-	void updatePreview() const;
+	void updatePreview();
 	///
 	bool canPreview() const;
 
 	/// contents
 	MathAtom par_;
-	/// LaTeX preview
-	mutable grfx::Loader loader_;
+	/// non owning pointer
+	mutable grfx::Loader * loader_;
 };
 #endif
diff --git a/src/mathed/formulabase.C b/src/mathed/formulabase.C
index c8e5f0f608..5961993563 100644
--- a/src/mathed/formulabase.C
+++ b/src/mathed/formulabase.C
@@ -158,8 +158,6 @@ void InsetFormulaBase::metrics(BufferView * bv) const
 	mi.base.font  = font_;
 	mi.base.font.setColor(LColor::math);
 	par()->metrics(mi);
-	if (lyxrc.preview)
-		updatePreview();
 }
 
 
diff --git a/src/mathed/formulabase.h b/src/mathed/formulabase.h
index d72e3fdb79..6732fe54f9 100644
--- a/src/mathed/formulabase.h
+++ b/src/mathed/formulabase.h
@@ -118,6 +118,8 @@ public:
 	virtual void revealCodes(BufferView *) const;
 	///
 	virtual Inset::EDITABLE editable() const { return HIGHLY_EDITABLE; }
+	///
+	virtual void updatePreview() {}
 
 
 private:
@@ -138,8 +140,6 @@ protected:
 	void metrics(BufferView * bv = 0) const;
 	///
 	void handleFont(BufferView * bv, string const & arg, string const & font);
-	///
-	virtual void updatePreview() const {}
 
 	///
 	mutable int xo_;
diff --git a/src/mathed/math_cursor.C b/src/mathed/math_cursor.C
index 32d6876b65..31dbb201a2 100644
--- a/src/mathed/math_cursor.C
+++ b/src/mathed/math_cursor.C
@@ -77,6 +77,14 @@ MathCursor::MathCursor(InsetFormulaBase * formula, bool front)
 }
 
 
+MathCursor::~MathCursor()
+{
+  // ensure that 'notifyCursorLeave' is called
+  while (popLeft())
+    ;
+}   
+
+
 void MathCursor::push(MathAtom & t)
 {
 	Cursor_.push_back(MathCursorPos(t.nucleus()));
@@ -103,8 +111,12 @@ void MathCursor::pushRight(MathAtom & t)
 bool MathCursor::popLeft()
 {
 	//cerr << "Leaving atom to the left\n";
-	if (depth() <= 1)
+	if (depth() <= 1) {
+		if (depth() == 1)
+			par()->notifyCursorLeaves();
 		return false;
+	}
+	par()->notifyCursorLeaves();
 	Cursor_.pop_back();
 	return true;
 }
@@ -113,8 +125,12 @@ bool MathCursor::popLeft()
 bool MathCursor::popRight()
 {
 	//cerr << "Leaving atom "; par()->write(cerr, false); cerr << " right\n";
-	if (depth() <= 1)
+	if (depth() <= 1) {
+		if (depth() == 1)
+			par()->notifyCursorLeaves();
 		return false;
+	}
+	par()->notifyCursorLeaves();
 	Cursor_.pop_back();
 	posRight();
 	return true;
diff --git a/src/mathed/math_cursor.h b/src/mathed/math_cursor.h
index aa9a15554d..f250c4975b 100644
--- a/src/mathed/math_cursor.h
+++ b/src/mathed/math_cursor.h
@@ -60,6 +60,8 @@ public:
 	///
 	explicit MathCursor(InsetFormulaBase *, bool left);
 	///
+	~MathCursor();
+	///
 	void insert(MathAtom const &);
 	///
 	void insert(MathArray const &);
diff --git a/src/mathed/math_inset.h b/src/mathed/math_inset.h
index 47f9b8bb9e..0c6fd08548 100644
--- a/src/mathed/math_inset.h
+++ b/src/mathed/math_inset.h
@@ -244,6 +244,8 @@ public:
 	virtual bool lock() const { return false; }
 	/// access to the lock (only nest array have one)
 	virtual void lock(bool) {}
+	/// get notification when the cursor leaves this inset
+	virtual void notifyCursorLeaves() {}
 
 	/// write LaTeX and Lyx code
 	virtual void write(WriteStream & os) const;
diff --git a/src/mathed/math_nestinset.C b/src/mathed/math_nestinset.C
index c67666853e..e724c37a94 100644
--- a/src/mathed/math_nestinset.C
+++ b/src/mathed/math_nestinset.C
@@ -5,6 +5,7 @@
 #include "math_nestinset.h"
 #include "math_cursor.h"
 #include "math_mathmlstream.h"
+#include "formulabase.h"
 #include "debug.h"
 #include "frontends/Painter.h"
 
@@ -234,3 +235,11 @@ MathArray MathNestInset::glue() const
 		ar.push_back(cell(i));
 	return ar;
 }
+
+
+void MathNestInset::notifyCursorLeaves()
+{
+	//lyxerr << "leaving " << *this << "\n";
+	if (mathcursor)
+		mathcursor->formula()->updatePreview();
+}
diff --git a/src/mathed/math_nestinset.h b/src/mathed/math_nestinset.h
index 64caa87a8e..e20cd31c9a 100644
--- a/src/mathed/math_nestinset.h
+++ b/src/mathed/math_nestinset.h
@@ -57,6 +57,8 @@ public:
 	bool lock() const;
 	/// access to the lock
 	void lock(bool);
+	/// get notification when the cursor leaves this inset
+	void notifyCursorLeaves();
 
 	/// direct access to the cell
 	MathArray & cell(idx_type);