One or More Pages Are In Use and Could Not Be Deleted

Explorer ,

I am a heavy user of the application, which although much improved, is still buggy. I frequently have issues where I am unable to delete pages. Usually this can be overcome by restarting the application. Today, I have a document which needs to go out and there appears to be no solution. I restart the application. Still a problem. I restart my computer. Still a problem. I leave the application open for hours. Still a problem. Can someone help??