Totalbiscuit has posted a notice on their front page explaining what happened -- sometime last week, a hacker attempted to post some kind of malware nonsense on their forums, and was headed off at the pass. Unfortunately, Google just happened to catch one look at a possibly negative piece of code, and thus the site was flagged (strange that just one flag would cause the kinds of alerts that Firefox is spitting out, but that's a discussion for another day). But at this point, we know for certain that there is no malicious code on WoW Radio, and even Google admits that the one piece of code it saw was the fault of a third party, not the WoW Radio folks.
Both Totalbiscuit and Duncor tell me they're working with their ISP and Google as much as they can to get the warnings removed. But in the meantime, you've got nothing to worry about -- you can listen to our podcast (or any of the other podcasts over there) without worry.