Question : Domain not available

I've got a new Win XP pro PC that I set up on our domain and everything worked fine.  When I set it up in the user's office, at first it logged on ok, but when I tried to set user rights on it, it said that there was no trust relationship with the domain.  I had experieneced this before, and set it to log on to workgroup instead of domain, then deleted the computer from AD, then rejoined the domain.  That went fine--it found the domain and set it up ok.  The next time I logged on, it says it can't log on because "domain is not available."  And yet if I log on to the local machine, I can ping the domain and browse the servers (by using the domain user name and password when it asks for it).  Why is the domain not available in this case?
This is urgent, so your help ASAP is appreciated.

Answer : Domain not available

Check the Networking Settings (IP, DNS, etc.) and enable NetBIOS . Reboot all.
Make sure that are you wait 15-30 min. for AD update !!! Before that, all modif. is not available !