There are a few things you can attempt, but I can't tell if any of them will work until you try.

Odds are they're blocking it. If they're doing that, they might have a phone number or email to complain about that. If they would care to, I wouldn't mind emailing them to find out what criteria they use for blocking stuff (I'd use it not just for PV, but for other sites I host/design).

If they're stubborn jerks, switch your PC's DNS to OpenDNS (www.opendns.com). Since they seem to be using DNS to block stuff, that will defeat their entire system.

Another possibility is to go to Hurricane Electric (he.net) and get yourself an IPv6, because those will be immune to both DNS and IP filtering. My servers are all IPv6 compliant.