User account locking out randomly

I have a user who’s network account is locking out randomly (Windows NT domain, XP workstation)

Indications are denial of printig services/exchange etc. When I check account via user manager on the server, the account has been locked out.

I’m confident the user is not mistyping the password, and the password has been set to never expire. Additionally, on occasion, the lockout has “fixed” itself, returning all services back to normal.

Has anyone seen this before, or have any advice on where to troubleshoot (I’d like to avoid creating a new user account).