The first could be a problem of hiding screen but having forms (by default) in screen, so you see nothing but the task can be found.
But the dbf corruption problem just from starting an exe. Well, what does it do? Do you have any initial routine of using some packing or automatic fixiing on tables, which, if started twice, could lead to problems?
I think we'd need to see your code to see what's going on, there is no generally known OS/runtime/VFP problem that fits our description.
Chriss