You are probably being affected by the MS RPC worm, try the following:
1a. Unplug your internet connection, boot up normally, run task manager, kill msblast.exe (if you don't see it, skip step 1b)
1b. Open regedit, goto HKEY_LOCAL_MACHINE>Software>Microsoft>
Windows>CurrentVersion>Run and delete: ”windows auto update" = MSBLAST.EXE
Another fix is to go into control panel, administrative tools (you have to be logged in as an admnistrator), services, find remote procedure call, goto the properties on it, select the recovery tab and select "take no action", then head over to
http://windows.microsoft.com and patch up quickly.
edit:the first step is the solution to remove the worm, the second one stops RPC from taking your machine with it when it crashes.