I can't believe I fell for it.
Got a BSOD with a very legit looking notice that Microsoft had locked the computer to prevent further damage. The OS is Windows 7 which I'm not really familiar with. I couldn't close the browser.
I called the customer service number and talked to the rep who asked a few basic questions. Then he said "there would be a fee to unlock the computer".
I had been had. First time ever.
Restarted the computer and cleared the cache. No problems since.