A couple of things to try...
1) Check for viruses
2) Upgrade video drivers
3) Upgrade (or maybe downgrade) printer drivers
4) Reinstall OS


>Thanks George for your response.
>
>No, there seems to be NO pattern to it. It just happens RANDOMLY when they open or close various forms in the application. Sometimes a print job may have been sent, and sometimes not. It happens up to 10 or 15 times a day on the affected computers, and of course customers lose everyting when it happens.
>
>Cyrus