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.

>>755
...Which is why a valiant few have traveled far and wide into the depths of IRC with the hope of finding the mythical creature known as "mod", and, with their silver tongue, persuade them of unblocking us until a few months later, when we are blocked again.

However, these heroes have all returned with nothing but failure and shame.