I installed MSE on several machines months ago, and these are legit systems with legit keys. However, as of today MSE is complaining.
Windows did not pass genuine validation. Security Essentials will
become disabled in 28 days if you do not resove this issue. To
continue using Security Essential, click Go online and resolve now and
get genuine Windows.
What would have caused this to happen?
EDIT: These systems have been running years and never had any problems. So I know the keys are legit.
Click Go Online like it says, one of the options should be to re-activate windows (likely over the phone). Explain over the phone that you have the CD keys, and those keys are in use on only one system per key (they are arn’t they?). You experienced a glitch, and because you are not breaking any licensing agreements they will give you a new activation code and everything will be back to normal.
If you are using the same key on multiple computers, the answer is you got caught and windows licensing is doing it’s job preventing that single key from being installed multiple locations concurrently.