Rendering issue on Windows 7

I have a strange issue. One of the end-users here is having a intermittent rendering issue in a proprietary program. I called their support, but it isn't a known issue. I can't reproduce it for them to remote in and see it. One fix was to exit and restart program, but it only last about 10 minutes before problem starts again. The other fix is to click the Full Screen icon (upper right) and click it again. The setup is a SFF ThinkCenter with dual monitors (one VGA, the other Display port). Any thoughts?