When I turned on this morning, I got an orange message in the bottom right hand corner saying something about having to validate the mse certificate or in would terminate in 30 days.
I pressed the validate now button and now I have a little box on the left saying 'legit(2). hta.
I assume that you have installed the Microsoft Security Essentials anti-virus program on your computer???
If you have go to the Microsoft web site (or put MSE into Google to find it) and see what it says on there. They should have a HELP section somewhere.