There's a long thread on Microsoft discussing the problem.
One solution which worked for quite a few people was to reboot, run CCLEANER then install (reinstall)
If you use REVO Uninstaller to remove MSE 2.x, you still need to run CCLEANER.
Worked for me under all flavors of Windows.
The Microsoft topic above has additional solutions, including a batch job to clean the registry (read thru, it's towards the end.
Anyway, it looks like it's a registry problem.
The MSE uninstall, like many many other apps, does a poor job cleaning after itself on uninstall.
Good luck.
OOPS. Here's the MS Support topic:
http://answers.microsoft.com/en-us/p...2-430f0ae7937c