I've seen something similiar. It occurred for me when I had an app that had an image and a container added to _screen, so I could have a nice background and buttons in the main VFP window. When I removed the items explicitly instead of waiting for CLEAR ALL to do it it solved the problem.

>After installing SP3, I've had major Win98 lockups related to vfp6 - worse than Blue Death Screen, just a total lockup, where the PC has to be switched off/on. Just before lockup, a messagebox "Explorer has performed an illegal operation..." This is a fairly new 450/128 machine, and this problem didn't exist before SP3...
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>This seems to occur when I run a vfp6 app, then close vfp6, then try to re-open vfp6 later, though sometimes while during a session. By (painful rebooting :) trial and error, it seems to be caused by CLEAR ALL at the end of app's main prg. I believe this is related to a similar C000005 error before SP3, except now the result is even worse :)
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>Anyone else seen this yet?