I'm not an admin so I can't say for sure, but here is what I think happened, if you look at the ban-list:
http://sourcebans.war-lords.net/index.php?p=banlist
18 people got banned at exactly 15:06 today.

So my guess is it was the MAP that was the problem. The server banned us all , and I was looking at the server in my servers list while new people would join and get banned.
Once the map changed people stopped getting banned.

So I'm thinking whoever cleans this problem up will probably need to unban everyone at 15:06 and after, and either fix (or remove) the map battlegrounds. (sorry I forget the exact name, it was awp_cmon_battlegrounds I think? something like that)