Copy the prefs from another account (or create one and use the defaults).
That should get you to where you were, unless you used a lot of non-default channels.
I've had Sherlock do this to me a few times, and this recovery method has worked.
Also, if you have .Mac Backup (or any other backup of your prefs), you might have a copy of the prefs eleswhere. That's preferable, since it would have your data in it as well as your channels.