I had it happen in subscriptions, New Posts, headphone buy/sell/trade forum.
Google flagged netseer as malware as the site was apparently hacked but their own Adsense product was still serving the ads.
Its affected a ton of sites, including New York Times, Huffington Post, etc
Usually refreshing the page a few times eventually got it to load without a problem but it hasn't happened in a few minutes now so maybe Adsense is fixed on Google's end.
Edit: btw, I'm using IE (at work). Apparently both IE and Firefox use Google's malware list so all three browsers will be affected. Not sure about Opera or Safari.
Edited by Jibrille - 2/4/13 at 9:46am