RPC problems could be the blaster virus on one of your servers. Also, a lot of virus scanners meant for client computers will screw up RPC or something on Windows 2000 servers and cause this. So don't just install a regular (non-server) version of Norton on a server- it can cause big problems. DNS could also be an issue as always run "netdiag" (get from Support Tools on the Windows 2000 CD) to see if it's DNS or not.