Tonight, I finally decided to fix a problem that has been bugging me. When I would compose an email message, I would see odd delays listing names in the autocomplete routines for addresses. So I would type in "and" and see a long delay (long enough for me to notice and be annoyed), then I would see the "andrew" email address autocompleted and alternate "andrew" emails listed. Then if I hit the down arrow to select another address I would see the same long delay - even though the information is already displayed.
This is a minor issue to be sure, but when you deal with a lot of email messages back and forth, this becomes annoying and time consuming. So it was time to fix this.
A quick search of Google for "slow address resolution in Thunderbird" lead me to this post: http://groups.google.com/group/mozilla.support.thunderbird/browse_thread.... The entire thread has some good ideas and tips in there, but the one that did the trick for me was to check for corrupted address book entries.
As it turns out, I didn't have any corrupted entries. BUT, I did have an LDAP server listed. And that LDAP server is no longer functional. So rather than edit my prefs.js file manually, I opened the AddressBook and deleted the suspect LDAP server entry. Right away my lookups became much quicker.
So if you are seeing slow lookups, check if you have any LDAP servers listed as alternate address books, and if so, make sure those servers are functioning properly.