Router blocks me from connecting to specific website

I finally figured out what’s been causing me problems with my router.

Background: ever since I upgraded to Vista, I haven’t been able to access www.washingtonmonthly.com from my home network. Works fine from an XP box on that network; works fine from work; works fine if I plug directly into an addressable IP.

Behavior: Sometimes I can ping www.washingtonlymonthly.com (74.2004.194.154), sometimes I can’t. Sometimes I can get the front page to start loading, at which it dies halfway through; sometimes I can’t. If can run a ping -t in the background while I load the website - about a second after the page starts to load, it stops responding.

Diagnosis: I was watching the logs on my new DGL-4500 (thanks wumpus!) and noticed this:

Fri Dec 14 19:43:34 2007 Blocked incoming ICMP error message (ICMP type 3) from 74.200.194.154 to 216.231.50.131 as there is no UDP session active between 216.231.50.131:500 and 74.200.194.154:500

Type 3 is destination unreachable. I have no idea what’s causing this - any guesses? Changing router settings seems to have no effect.

Never mind, figured it out. According to netmon, my box sends out AuthIP and IKE requests to everything - and for some reason, this one target machine goes haywire when it gets them. Just had to exempt them.