I keep getting the “Why am I being redirected here?” Firewall page

When I log in, I keep seeing the page mentioned in the title (http://www.planetvb.com/error.php?c=1) instead of the front page. I haven’t changed any of my firewall settings, and I’m not trying to register, anyway. I don’t run an adblocker (except for a hosts file, which I also haven’t changed recently, and shouldn’t affect PVB, anyway).

I tried deleting all my PVB cookies, and it didn’t help.