Force Infrastructure Operations Master Role seizure
After raising the domain and forest functional level to Windows 2003, one of our Global Catalog Servers upon reboot started complaining that it should not be the Infrastructure Operations Master as well. It was also for some sites the only configured DNS server. Even after seizing the role from another server, the original server claimed to have the role of IOM. We removed the Global Catalog role, and then forced the original server to seize the IOM role successfully and all was well again.
This fixed it.
Microsoft Windows 2000 Advanced Server Documentation