It sounds like a problem with a mouse driver. Take a look at Thread #307627 that discussed a similar problem.

>I've been running a VFP 6.0 executable program for over a year on different operating systems, from Win95 - Win2000 and NT 4.
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>Recently a client bought a Sony notebook with Windows 2000 Professional. The exe file runs great but once in a while as the mouse is moved the program shots down with no warning (it just disappears off the screen). I run Windows 2000 Professional on my DELL notebook and I've never encounter this problem.
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>I have downloaded SP5 for VFP 6.0 but the problem still persists.
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>My client uses a Logitec Cordless TrackMan Wheel (mouse), I don't know if this makes a difference. He says that this does not happen on any other program that he runs only on my VFP 6 executable program.
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>If anyone has any suggestions please let me know.
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>Thanks
>
>Louis