Problem with writing memo from address book

I have one user that when they open one of our client address books, and clicks Write Memo, they get these 2 errors:

Error. Your mail file could not be opened. Please verify that it appears correctly in your location.

Then,

Object Variable not set.

How do I fix this? They can open their mailfile off the server with no problems.

Thanks!

Michael

Subject: Have them edit their Location document and verify that the Mail Server and Mail File are correct.

Subject: RE: Have them edit their Location document and verify that the Mail Server and Mail File are correct.

I have verified this to be correct. Is there anything else I can check?

Thanks!

Michael