UserID issue

Hi,

Running Filr 1.0.1.65 in a small deployment in Xen.

I deleted a user (yes, I know I should have disabled them) and then re-created the account and now the user cannot login.
If I re-create the user with a new UserID, then he can login. How can I delete/purge the old UserID so I can recreate the user with the old UserID?

Regards
John