I never meet this problem but you can:

A. Start your computer, when the error appears press the start button and write "Snipping tool" in the search box without the quotes. With snipping tool make a picture, upload it to your favorite image hosting site and give us a link. If you don't know how to upload an image tell us and will gladly help.

Fix#I
1. Go to http://www.vista4beginners.com/Windows-Update or http://www.vista4beginners.com/Windows-Defender and download new definitions related to defender. If the problem occurs even after you did this then it's not related to defender.
2. This should be done only if you have another firewall & antivirus. Just go to http://www.vista4beginners.com/How-to-disable-Windows-Defender and disable it. If the error doesn't appear after restart then defender is the problem maker. If he is, then make sure you redo step (1), or you've done step (1). After new definitions have been downloaded, activate defender again (if you still plan to use it) and restart. If you get the same error then you can either disable it, ignore it or contact Microsoft for support.
Fix#II - There is no fix no 2 for the moment because I'm assuming defender is causing your problem.
If it's not then will exclude it from the list (program causing problem list). The next step, if Fix#I wasn't helpful, will be done after you've done point A.

Hope this helped.