outlook 2003 error message with contacts

[jsltd]

Hi,
My set-up is outlook 2003 using an exchnage email account. windows xp sp2.

I seem to have a problem with my contacts in Outlook, when trying to add
detail to a contact or a new contact I get the following message. 'The
message interface has returned an unknown error. If the problem persists,
restart Outlook' I have restarted on numerous occasions and rebooted my
machine.

I noticed it when I was trying to add an email address in contacts. I then
free typed the name in the To: box of an email but the same message occurs.
Have you got any ideas why this is happening as it is stopping me updating
contacts or emailing this person whome I want to add an email in their
contact file ?

Thanks in advance.