If you have a domain controller in the environment and the original role holder is NEVER returning to the AD forest with the same name, SEIZE the FSMO roles using the steps at http://support.microsoft.com/kb/255504.
Note that you will need to preform a metadata cleanup after performing this operation.
When you repair the original domain controller, you MUST rename it and then DCPROMO it into the forest.
Note that if you are running Small Business Server edition, none of this is going to work as you can only have one DC in the domain/forest. In this scenario, you must do an Active Directory recovery.