I am writing some software that has a main dialog with a couple of tree controls and some bitmaps. The app works fine for 15 or 20 minutes of use at a time and then the controls and bitmaps stop getting repainted properly. For example, if I click on the tree control to expand a branch it appears to be doing it but instead of it appearing on the screen the rectangle that would contain the updated painted region gets painted gets erased. From then on any activity that causes a region to be repainted gets erased. For example, if I bring another window to the top, covering the app, then bring the app back to the top all of the tree graphics and the bitmaps on the dialog are erased. No errors are displayed. If I exit the code and start it up again the erased sections are still erased. Nothing short of rebooting has cleared up the problem. Any ideas?