That usually means you have a corrupt Outlook profile. Create a new one with
a unique name. Then look for the NK2 file from your old profile and rename
it to match the NK2 file of the new profile.

Signature
Russ Valentine
[MVP-Outlook]
> Hello,
> I had a whole bunch of e-mail addresses that would complete automatically
> when I started typing the first few letters of a person's name or e-mail
> address in the "To:" field. Well... they are all gone!!! I don't know
> why.
> It just happened. How do I get them back?