No Start Menu, DNS console fails

One of my Win2K servers has developed a strange behavior. When I click on Start, no menu pops up. When I open the DNS management snap-in in administrative tools, I get an error message about CLSID blah-blah-blah. When I close that, I get an empty DNS management console window. Restarting the server fixes both problems, but only temporarily.
This server has been running reliably since last June, and has all the latest updates. It’s also protected by Norton AV.
Anybody have any ideas?