[quote=@TheUnknowable]
Yesterday and today I left my page on the Subscriptions tab so that I can just hit "reload" to check for updates.

But a few minutes later it changed to one of those fake "You've got a virus" ads.

I'd guess it's a problem with the banner ads loading unsafe sites, but don't know for sure.
[/quote]

The banner ads are supplied by Google's Adsense so they shouldn't cause an issue with a potential virus threat. They also are designed RP work off your search history so I know I tend to get a bit of gaming and RC car ads on mine. You can usually report those ads that tend to be a bit off and unusual by clicking on the corner of the ad itself. 

I would suggest using a virus scanner in your computer first because I would suspect that you have a Trojan installed. ESET is pretty good and is non invasive like what McAfee or Norton have become, and I believe Malware Bytes is still a good recommendation... But I haven't had to look at that for a while.