Forms not saving

I upgraded a Access 2003 MDB to Access 2007 accdb format. I've tried to make
some modifications to some form designs, but the forms will not save the
design changes. When I close the form I am prompted if I want to save the
changes and when I say yes the dialog box goes away, but the form stays
visible and the changes are not saved. I get no error messages. The only way
to close the form is to click no when promted to save changes.
I can create and save new forms without a problem. I can also save and
modify data without any issues.
Can anyone help me?