If you receive the subject message when trying to log on locally, it may be due to a memory leak.
Network users may receive a RPC Server Busy or similar RPC error.
If you have the Shut Down button on the Windows NT Security dialogue, you can shutdown to temporarily elleviate the problem. If no Shut Down button is available, you will have to use SHUTDOWN.EXE.
If you can't, try tip 0182.
NOTE You can use Regedt32 on another Windows NT computer to Select Computer, instead of REG.