We integrated a new windows 2008 server about a year ago and kept the old 2003 server online for backup DNS and authentication. However, if the old server goes off line, all the workstation can no longer log into the domain. any attempt gets this error.
"A domain controller could not be contacted for the domain that contains an account for this computer"
Then if I turn the old controller back on, they can all log in. I checked all the FSMO roles and they are all on the new 2008 server. DNS seems to be working fine. NSlookup all point to the new server.