"There was no entry in our database for your ban. Therefore, the reason for this ban cannot be automatically determined. It is likely that your ISP is caching a ban intended for someone else. Please contact a moderator on #4chan @ irc.rizon.net with your IP address (IP adress) for more details. Moderators are channel ops (@) and half-ops (%)."
I have the same problem, guys. Since 1-18-2012, I can access all the other boards, but I just can't access /a/. This is painful for me, because I'm an animu fan, and 4chan's /a/ is probably the best place on the internet to discuss animu.
I still haven't tried doing a DNS flush yet. Maybe that will fix it.
I still might try to get on 4chan's Rizon chat. Shouldn't the mods be able to fix it for you personally if you give them your IP address?