this is my 2 cents.
I had a similar problem about 1 year ago. It was caused by me trying to run the form in one instance of VFP while the form was being saved in another. If something similar happend to you. You might be able to recover an old version of the form by looking in the directory the form was in and searching for a strange named file something like r0098uwiu7.tmp. (This file I think is created right before you resave a file--its a copy of the old version that is deleted after a successful save). Open this file as a form of course . Otherwise a rewrite is in order.