If you're on a machine that doesn't have any important tournaments on it, can you try this:
1. Uninstall WER. If you download the WER installer and run it again, it should give you the option to remove it. Otherwise, the Programs and Features control panel should be able to get it uninstalled.
2. Inside this directory on your computer:
C:\Users\\AppData\Roaming\Wizards of the Coast\
(AppData is hidden -
here's how to see it)
If it is there, rename the “Event Reporter” folder to something like “Event Reporter (old)”
3. Reinstall WER.
This could theoretically fix:
1. The WER install having issues.
2. The WER database being corrupt.
I'd recommend what Jean-Francois said as well - make sure your computer has all required and optional updates installed, just to eliminate the possibility of some random .NET installation not being on the machine.
One other thing to try, just for the sake of being thorough: right click on the tile or application in “All Apps” and select “Run As Administrator”; that would at least eliminate a possible permissions issue.