Okay know I understand,

First of all I've already reinstall my VFP 5.0.
Second, No the problem does not occur in all the forms, only in some and I don't know why.
Third, Now its not just me whose experiencing that problem but my co-programmer to.
I have already checked the things that you have told me and they are fine.
I've already rewritten some of the program but the problem is still there.