The request lookup key was not found in any active activation context

This probably happened when an Internet Explorer 7 update was installed, either by you intentionally or automatically. First step: restart your machine and see if it goes away. If this doesn't work, you'll need to uninstall and reinstall Internet Explorer 7 - if this is too much for you, you may want to have it fixed at a computer store.

See this thread for more detailed info on the problem and the fix.

Vasily