ISP blocked due to abuse?

Well, it seems today that I'm now unable to post anything over at the 4chan imageboards, otherwise I get this message:
"Posting from your ISP has been blocked due to abuse. [More Info]"
I can still browse the site, all the images and threads load fine, I just can't post. What gives? I've never posted spam or porn.

Hmm, I don't if this would work. We have dynamic IPs so they'd have to unban a shitload of IPs. And did they really ban the first 2 numbers of the IP? Maybe they just banned IPs that seem to come from Egypt and Romania.