Suddenly my legitimate Win7 Pro popped up a message saying it was not genuine, and I needed to reactivate.

I reentered my product key, and it said that it was no good, and directed me to go online to purchase a new product key!

I was getting ready to raise hell with someone, when I retried the product activation wizard after rebooting, and it finally re-activated my copy.

Has anyone else experienced this?  What could be the cause?