I was using Google Chrome on an HP Envy when this happened. I am told that the "freezeup" is likely to be a browser problem and not a true threat. I will check further with Webroot, Google, and possibly CERT for more information on the problem. I didn't try this on other browsers, but it may not be reproducible according to what I was told. One interesting observation: after Restart, Chrome didn't say it was improperly shut down, as it often does. But after Restart, and closing everything and reopneing. everything worked normally.
The "web page" may well have been associated with a "tech support" scam where the consumer is supposed to call an 800 number to unlock a computer (but paying in bitcoin sounds rather unlikely). I've gotten repeated landline calls from one number in India known to be associated with a "tech support" scam. I don't answer robocalls.