Blimey DS, that's bad.
Yes, there were a few times when a popup came up giving only the option of pressing "OK". I can't remember what the popup said, but I think it went on about "your computer needs tuning up. click here to do so" or something.
I couldn't cancel it or close the popup down, even with using Alt+F4, so in these cases I always finish what I'm doing then use the task manager (ctrl+alt+del) to End Task the browser. This way you're not forced to press OK on the popup.
Also, try using the Avast (Personal edition) anti-virus:
www.Avast.com It's free for home users.
I've had viruses before where my other antivirus (previously AVG) couldn't contain/quarantine them, forcing me to do an OS re-install. But Avast has stopped any virus attacks dead in its tracks, it's a great program. However, I've only had five viruses since I've used PCs since 1998 as I've tried to use caution where possible (after reading others experiences), but the first two was when I used AVG and needed a complete OS reinstall each time. I then ditched AVG and started using Avast, and the last three viruses were stopped dead and killed by Avast.
Avast is more system resource intensive, and manual scans take longer, but I've never heard a bad word said against it regards its virus protection. As far as I can gather it's top-notch.
However, I have to disable it when tracking on music programs as my ASIO performance suffers with clicks/pops here and there when using ultra-low latencies, but I'm never on the 'net when tracking anyway so it's no biggie to disable it then.