It's not a universal problem, so it could well be some network issue. Some peer connection between ISP A and ISP B gets gumped, and you get a mess of people who can't get to [insert their favorite site here] when everyone else in the world can just fine.
I can get on there just fine. As was said earlier, it's likely a problem at your ISP or at another location along the network. It isn't a problem with wizards.com itself.
I wasn't able to get on a while back. I didn't do anything to clear cache or anything, but was able to get onto the site a little later. I wonder if they are doing some server maintenance and so can't handle all of the volume, especially if it is high with people checking in looking for a GenCon announcement.