reverted:
--- src/viscontrol.cpp	Fri Aug 12 23:18:47 2011 +0100
+++ src/viscontrol.cpp	Sat Aug 13 01:27:01 2011 +0100
@@ -670,15 +671,24 @@
 					continue;
 
 
+				//Initially assume that everything is passed through
+				//filter
+				int blockMask=0x0;
+
-				int blockMask=0xFFFF;
 
 				if((*it)->haveCache())
 				{
 					//Loop over the children of this filter, grab their block masks
 					for(tree<Filter *>::sibling_iterator itJ=it.begin(); itJ!=it.end();itJ++)
 					{
+
 						if((*itJ)->haveCache())
+						{
+							int curBlockMask;
+							curBlockMask=(*itJ)->getRefreshBlockMask();
+							blockMask= (blockMask & curBlockMask);
+
+						}
-							blockMask&=(*itJ)->getRefreshBlockMask();
 						else
 						{
 							blockMask&=0;