Access 2003 ADP – Unexpected Error on Save

I’ve inherited a problem that is making me cuss. I have an Access 2003 ADP file that can not be saved. Add a line of code or a comment or drag a button, then ‘File -> Save’; you end up with the ‘Unexpected Error. Send to Microsoft Y/N’ screen. It will try to repair the database by default.
I’ve been told this started when SP2 was rolled out on Windows XP, but I’m not sure about that and I havn’t seen anything on the web suggesting that.
Any seen this or something similar?
p.s. Access is not my forte.
Thanks