Did you ever get an answer for this?  I did the same thing with the same results.  Changed from domain to workgroup, it asked to reboot, and from that point can't log in with the same password (can't log in period).  I changed to workgroup so I could connect to home printer with my work laptop.
   
    ----- John Cooper wrote: -----
   
    A client running XP Pro changed her logon credentials
    from a domain to a group (so she says)  Now her original
    password doesn't work.  ANy solutions?
   
    Thanks