domain controller

Recently I have migrated from sbs W2K to sbs W2k3. I had everything up and running smoothly for about a week and I installed the latest updates. Now anyone on outlook 2k3 cannot see the server. Everything else works fine and computers with outlook 2k2 can see their email just fine. I looked in the log file of one of the computers that would not work and found that the group policy could update in the time allowed. Also before that logged an error that says could not locate domain controller. I unjoined the computer from the domain and tried to rejoin to the domain. I get the error ?A socket operation was attempted to an unreachable host. Does anyone know how to roll back updates? Or have any other idea what could be going on!