Strange Failure

April 2011 Problem with Lenovo X61 Tablet: Runs Windows 7 Professional with 3 GB Ram, 85GB Harddrive Intel Core 2 Duo CPU L7500 1.6p Ghz.
Problem: All of the icons on the Task Bar and the left side of the Start Menu have stopped working under certain conditions.
More Specific Symptoms: Clicking the icons of the applications that have been pinned to the task bar fail – it results in the white x on in red circle error with path stating: “application not found”. The app can be opened from the task bar if you right click and then choose a recent file from the list. This works with Excel, and Word, but not Firefox. For the Start Menu, everything in the dark gray area seems to work fine, but clicking the icons for the apps of the left side gets the same white x error. The apps that allow you to recall the name of a recent file will result in opening up the app by way of opening that file first. The surest way of opening the app is to find it using Windows Explorer, right click and then use “Start” and “Run as Administrator”. Using “Open” does not work. It gets a window “Open with”, “Choose the program …” with a list of applications that do not open the file/app.
Attempted Solutions To Date: Run AVG Internet Security (their top package which includes antivirus) ver. 10. Run SuperAntiSpyware. Reinstalled Windows 7 Professional. No change whatsoever in the problem.
I have no idea what else to do. Please, any advice is appreciated.

Shawn or Brink,
Thank you very much. The problem seems to be fixed. I'm going to be watching to see if it comes back. Thanks again.
John (Jag)