Ok, that was the worm fix, here is the solution to the computer-shutting-down problem:

Go to your Services panel (Control Panel -> Administrative Tools -> Services or Start->Run->type services.msc, click OK), find Remote Procedure Call, right-click and select Properties, click Recovery tab, change "Shut down" to "Take no action" and Apply, OK.

I'm amazed how fast these things spread and are then recognized as threats. This morning when it happened to me twice scans came up clean. Don't know what time today msblast.exe was added to virus definitions.