The regular "Foxpro error" was repaired in version 2.9. Since you are running 3.1, I am guessing that something has happened in the Windows environment or that something running in the background is trying to access memory, which sometimes causes a GP fault. Sometimes it's a video card or new driver. Have you added anything new lately? Have you tried to restart Windows fresh?
You might change the video driver from the Program Manager and see if that helps. Perhaps others have ideas, too.