>A customer described to me that sometimes when he starts my VFP 9 application, almost right away the application main windows starts "jumping and shaking" (these are his words). He says that the only way he can stop this is by going to the Task Manager. How can I determine what would cause this problem?
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>Any suggestions would be greatly appreciated.

If they have a digital camera or camcorder they could make a small movie of the problem and e-mail it to you. This can be done in minutes with some cameras e.g. my Canon A75 saves directly to an .AVI file which is suitable for e-mailing once downloaded from the camera.

Another thing that can be useful for troubleshooting is to get them to set up a free trial GoToMyPC subscription on that PC. If they then give you the passwords you can see their system for yourself. In this particular case it might not show you "shaking" but it could be very useful in other ways, and possibly to let you directly fix a problem on their machine.