Ever have a machine tell you it's lost it's trust relationship when you try to log into it?

That's an easy fix! This happens when a machine in an Active Directory domain either has been offline for an extended period of time (I think the default is 60 days if I remember correctly), or another machine has been added to the domain with the same name...

You see, each object in an Active Directory domain has what's known as a SID or Security IDentifier. This SID uniquily identifies an individual object to AD and when an additional object of the same name is added to Active Directory, it overwrites the original SID with a new one (hense the old one becomes obsolite). Also, if a machine hasn't contacted AD within 60 days, the password that is automatically generated and maintained by the network, the machine and AD can expire.

Either way, the solution is to log in locally to the machine (you can find all sorts of help on the net on how to do that), remove the machine from the domain (reboot), rename it if there is another one with the same name (reboot), and then add it back to the domain(reboot). If the person who couldn't log in because of this had a domain profile on the machine before, it will still be there after you take the machine out and put it back in. That's because the profile is associated with the unique SID of the persons Active Directory account and that isn't changing (just the machine SID).