Do you even use an LDAP? If not, you migrated your settings incorrectly.
Remove the LDAP reference and enable the Outlook Address Book instead.
http://support.microsoft.com/kb/836205/en-us

Signature
Russ Valentine
[MVP-Outlook]
> When I create new email message and click the "To" I get an error message
> as
> follows: "Can't contact LDAP Directory Server (81)". What does this
> message
> mean? I just upgraded from Outlook 2000 to 2003. My contact list is
> complete, but my address book is empty. Please help!