Héctor:

This problem can be cause by other problem like corruption in the form and also the resource file. Try to open the form as a Table copie to another temp file. Delete the old and rename the temp file to the correct name. Sometime the memo files get corrupted and cause the C5 error. The same happend with the resource file. IN this case delete your resource file. Look for foxuser in all your computer and delete all.

Hope this fix your problem.