Welcome mnoman to the windows 7 forums.
There is a distinct possibility that your install went astray due to a corrupted mse.
Can we assume that you downloaded from the microsoft security site?
If you can do a restore back to an earlier time prior to trying to install mse.
This might be your best bet as it looks like your registry might have gotten munged up.
Also, do you have another AV or Internet Security product installed?
If so, then that could be the culprit.
PS:you might want to complete your system specifications also. helps..