Same thing here after I installed the initial scan to get Windows 7 update.
TEMPORARY FIX:
Open Task Manager (Ctrl+Alt+Del, click Start Task Manager)
Click on the PROCESSES tab
Find the "explorer.exe" under IMAGE Name and click on it
Click "End Process" (Lower right corner) (This closes the previous explorer desktop)
Click on FILE (upper left corner)
Click on NEW TASK
Type in "explorer"
Hit OK button
I've also noticed that if I close out all of my applications and then put machine into sleep mode, when I wake it, the task bar is still active. If my machine starts the screen saver or is left idle too long, my task bar disappears again.
COME ON GUYS: FIX THIS PROBLEM!!! I"m tired of the work around.
I AGREE... IT DOES WORK BUT WHY DOES THIS HAPPEN?? PLEASE FIX THE ISSUE.. IT IS VERY ANNOYING AND DISAPPOINTING SINCE I UPGRADED TO WIN7... SHOULDA SWITCHED TO A MAC!