diff --git a/indra/newview/llvieweroctree.cpp b/indra/newview/llvieweroctree.cpp
index e1684c19df2dd183cf4d7a20b875c28671590f92..e8eba432428330023c923b5c9ee6814fbb9191a1 100644
--- a/indra/newview/llvieweroctree.cpp
+++ b/indra/newview/llvieweroctree.cpp
@@ -809,7 +809,14 @@ class LLSpatialSetOcclusionState : public OctreeTraveler
 public:
 	U32 mState;
 	LLSpatialSetOcclusionState(U32 state) : mState(state) { }
-	virtual void visit(const OctreeNode* branch) { ((LLOcclusionCullingGroup*) branch->getListener(0))->setOcclusionState(mState); }	
+	virtual void visit(const OctreeNode* branch) 
+	{ 
+		LLOcclusionCullingGroup* group = (LLOcclusionCullingGroup*)branch->getListener(0);
+		if(group)
+		{
+			group->setOcclusionState(mState); 
+		}
+	}
 };
 
 class LLSpatialSetOcclusionStateDiff : public LLSpatialSetOcclusionState
@@ -821,7 +828,7 @@ class LLSpatialSetOcclusionStateDiff : public LLSpatialSetOcclusionState
 	{
 		LLOcclusionCullingGroup* group = (LLOcclusionCullingGroup*) n->getListener(0);
 		
-		if (!group->isOcclusionState(mState))
+		if (group && !group->isOcclusionState(mState))
 		{
 			OctreeTraveler::traverse(n);
 		}
@@ -945,7 +952,14 @@ class LLSpatialClearOcclusionState : public OctreeTraveler
 	U32 mState;
 	
 	LLSpatialClearOcclusionState(U32 state) : mState(state) { }
-	virtual void visit(const OctreeNode* branch) { ((LLOcclusionCullingGroup*) branch->getListener(0))->clearOcclusionState(mState); }
+	virtual void visit(const OctreeNode* branch) 
+	{ 
+		LLOcclusionCullingGroup* group = (LLOcclusionCullingGroup*)branch->getListener(0);
+		if(group)
+		{
+			group->clearOcclusionState(mState); 
+		}
+	}
 };
 
 class LLSpatialClearOcclusionStateDiff : public LLSpatialClearOcclusionState
diff --git a/indra/newview/llviewerregion.cpp b/indra/newview/llviewerregion.cpp
index 18232e75c97148d2e874b54562ab45183d3cb0a4..0c2c2365c7d7a493175243945bc9e372cd395be7 100755
--- a/indra/newview/llviewerregion.cpp
+++ b/indra/newview/llviewerregion.cpp
@@ -1183,6 +1183,9 @@ void LLViewerRegion::clearCachedVisibleObjects()
 	mImpl->mWaitingList.clear();
 	mImpl->mVisibleGroups.clear();
 
+	//reset all occluders
+	mImpl->mVOCachePartition->resetOccluders();
+
 	//clean visible entries
 	for(LLVOCacheEntry::vocache_entry_set_t::iterator iter = mImpl->mVisibleEntries.begin(); iter != mImpl->mVisibleEntries.end();)
 	{