Restart your computer and get into safe mode by holding down on F8.
More details are available here:
http://support.microsoft.com/kb/315222
Do a virus scan if you can from the safe mode boot. You won't have access to the internet, so you can head to bed.
Finally, drag your pointer to the very bottom of the screen. While pressing the left mouse button, drag your mouse upward. This may fix your "Start" button problem.
Thanks, Scott. I'll try that. I remember going into safe mode via MSCONFIG, at times, but I can't even get into start > "run" right now. Even the volume icon near the clock doesn't work.