--- svl/source/items/style.cxx	(revision 1348808)
+++ svl/source/items/style.cxx	(working copy)
@@ -806,14 +806,19 @@ 
 			// Alle Styles umsetzen, deren Parent dieser hier ist
 			ChangeParent( p->GetName(), p->GetParent() );
 
-			com::sun::star::uno::Reference< com::sun::star::lang::XComponent > xComp( static_cast< ::cppu::OWeakObject* >((*aIter).get()), com::sun::star::uno::UNO_QUERY );
-			if( xComp.is() ) try
-			{
-				xComp->dispose();
-			}
-			catch( com::sun::star::uno::Exception& )
-			{
-			}
+            // #120015# Do not dispose, the removed StyleSheet may still be used in
+            // existing SdrUndoAttrObj incarnations. Rely on refcounting for disposal,
+            // this works well under normal conditions (checked breaking and counting
+            // on SfxStyleSheetBase constructors and destructors)
+            //
+			// com::sun::star::uno::Reference< com::sun::star::lang::XComponent > xComp( static_cast< ::cppu::OWeakObject* >((*aIter).get()), com::sun::star::uno::UNO_QUERY );
+			// if( xComp.is() ) try
+			// {
+			// 	xComp->dispose();
+			// }
+			// catch( com::sun::star::uno::Exception& )
+			// {
+			// }
 
 			aStyles.erase(aIter);
 			Broadcast( SfxStyleSheetHint( SFX_STYLESHEET_ERASED, *p ) );
--- svx/source/svdraw/svdundo.cxx	(revision 1348808)
+++ svx/source/svdraw/svdundo.cxx	(working copy)
@@ -290,14 +290,29 @@ 
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+void SdrUndoAttrObj::ensureStyleSheetInStyleSheetPool(SfxStyleSheetBasePool& rStyleSheetPool, SfxStyleSheet& rSheet)
+{
+    SfxStyleSheetBase* pThere = rStyleSheetPool.Find(rSheet.GetName(), rSheet.GetFamily());
+
+    if(!pThere)
+    {
+        // re-insert remembered style which was removed in the meantime. To do this
+        // without assertion, do it without parent and set parent after insertion
+        const UniString aParent(rSheet.GetParent());
+        
+        rSheet.SetParent(UniString());
+        rStyleSheetPool.Insert(&rSheet);
+        rSheet.SetParent(aParent);
+    }
+}
+
 SdrUndoAttrObj::SdrUndoAttrObj(SdrObject& rNewObj, FASTBOOL bStyleSheet1, FASTBOOL bSaveText)
 :	SdrUndoObj(rNewObj),
 	pUndoSet(NULL),
 	pRedoSet(NULL),
 	pRepeatSet(NULL),
-	pUndoStyleSheet(NULL),
-	pRedoStyleSheet(NULL),
-	pRepeatStyleSheet(NULL),
+    mxUndoStyleSheet(),
+    mxRedoStyleSheet(),
 	bHaveToTakeRedoSet(sal_True),
 	pTextUndo(NULL),
 
@@ -335,7 +350,7 @@ 
 		pUndoSet = new SfxItemSet(pObj->GetMergedItemSet());
 
 		if(bStyleSheet)
-			pUndoStyleSheet = pObj->GetStyleSheet();
+            mxUndoStyleSheet = pObj->GetStyleSheet();
 
 		if(bSaveText)
 		{
@@ -394,7 +409,7 @@ 
 			pRedoSet = new SfxItemSet(pObj->GetMergedItemSet());
 
 			if(bStyleSheet)
-				pRedoStyleSheet=pObj->GetStyleSheet();
+				mxRedoStyleSheet = pObj->GetStyleSheet();
 
 			if(pTextUndo)
 			{
@@ -408,8 +423,18 @@ 
 
 		if(bStyleSheet)
 		{
-			pRedoStyleSheet = pObj->GetStyleSheet();
-			pObj->SetStyleSheet(pUndoStyleSheet, sal_True);
+			mxRedoStyleSheet = pObj->GetStyleSheet();
+            SfxStyleSheet* pSheet = dynamic_cast< SfxStyleSheet* >(mxUndoStyleSheet.get());
+
+            if(pSheet && pObj->GetModel() && pObj->GetModel()->GetStyleSheetPool())
+            {
+                ensureStyleSheetInStyleSheetPool(*pObj->GetModel()->GetStyleSheetPool(), *pSheet);
+    			pObj->SetStyleSheet(pSheet, sal_True);
+            }
+            else
+            {
+                OSL_ENSURE(false, "OOps, something went wrong in SdrUndoAttrObj (!)");
+            }
 		}
 
 		sdr::properties::ItemChangeBroadcaster aItemChange(*pObj);
@@ -482,8 +507,18 @@ 
 	{
 		if(bStyleSheet)
 		{
-			pUndoStyleSheet = pObj->GetStyleSheet();
-			pObj->SetStyleSheet(pRedoStyleSheet, sal_True);
+            mxUndoStyleSheet = pObj->GetStyleSheet();
+            SfxStyleSheet* pSheet = dynamic_cast< SfxStyleSheet* >(mxRedoStyleSheet.get());
+
+            if(pSheet && pObj->GetModel() && pObj->GetModel()->GetStyleSheetPool())
+            {
+                ensureStyleSheetInStyleSheetPool(*pObj->GetModel()->GetStyleSheetPool(), *pSheet);
+			    pObj->SetStyleSheet(pSheet, sal_True);
+            }
+            else
+            {
+                OSL_ENSURE(false, "OOps, something went wrong in SdrUndoAttrObj (!)");
+            }
 		}
 
 		sdr::properties::ItemChangeBroadcaster aItemChange(*pObj);
--- svx/inc/svx/svdundo.hxx	(revision 1348808)
+++ svx/inc/svx/svdundo.hxx	(working copy)
@@ -33,6 +33,7 @@ 
 #include <svx/svdtypes.hxx> // fuer enum RepeatFuncts
 #include <svx/svdsob.hxx>
 #include "svx/svxdllapi.h"
+#include <svl/style.hxx>
 
 //************************************************************
 //   Vorausdeklarationen
@@ -166,9 +167,8 @@ 
 	SfxItemSet*					pRepeatSet;
 
 	// oder besser den StyleSheetNamen merken?
-	SfxStyleSheet*				pUndoStyleSheet;
-	SfxStyleSheet*				pRedoStyleSheet;
-	SfxStyleSheet*				pRepeatStyleSheet;
+    rtl::Reference< SfxStyleSheetBase > mxUndoStyleSheet;
+    rtl::Reference< SfxStyleSheetBase > mxRedoStyleSheet;
 	FASTBOOL					bStyleSheet;
 	FASTBOOL					bHaveToTakeRedoSet;
 
@@ -181,6 +181,9 @@ 
 	// Wenn sich um ein Gruppenobjekt handelt:
 	SdrUndoGroup*				pUndoGroup;
 
+    // helper to ensure StyleSheet is in pool (provided by SdrModel from SdrObject)
+    void ensureStyleSheetInStyleSheetPool(SfxStyleSheetBasePool& rStyleSheetPool, SfxStyleSheet& rSheet);
+
 public:
 	SdrUndoAttrObj(SdrObject& rNewObj, FASTBOOL bStyleSheet1=sal_False, FASTBOOL bSaveText=sal_False);
 	virtual ~SdrUndoAttrObj();