I have Adblock Plus installed, but with csnbbs.com whitelisted. Your ads appear just fine.

I only use one forum, which I have bookmarked:

http://csnbbs.com/forumdisplay.php?fid=444

When I go to that page directly, I get your ad, immediately followed by your "Don't use adblocker!!!" message right below it. So it seems to be detecting the presence of Adblock Plus, but not detecting the fact that your ad is being displayed correctly.

If I then hit a different part of the site, it clears the adblock message, and I can return to the Rice board without seeing it anymore.

So it appears that your adblock detection logic is broken if a user goes directly to a bookmarked forum. (or at the very least, if you go directly to the Rice forum)