Cannot update field in form

[Cynthia]

I have created a simple form and cannot update the fields. This is a linked
table, I went back to the table and found I cannot update any fields in the
table I g et the following error:

This record has been changed by another user since you stared editing it.
If you save the record you will overwrite the changes the other user made.

I have the choice of copy to clipboard or Drop Changes.

I did not have this problem before we upgraded to Access 2007. I tried
deleting the table and relinking it, but still not working.

I would appreciate any help in resolving this issue.