modelsim wave view corrupt when detached

I am having problems with the wave view in modelsim version 6.6c (quartus 10.1) on XP 32 bit. Sometimes the section of the window that displays the waveforms does not update. Instead i see what was left by the last thing that had focus on the desktop. Also, I get 'CreateBitmap failed with code 8' in the console window that opens with modelsim. I have completely uninstalled all versions of modelsim and re-installed with no success. Does anybody have a clue about what is going on and how to correct it?