Ok, i'm going to explain you.
MCBan is a plugin installed in this server, wich registers all the bans in the servers wich have the plugin, so if you were banned in another servers globally, MCBan auto-bans you when you enter the server.
I think you were banned in other/s server/s and now MCBan is making his function e_e
If you weren't banned before, it would be a bug. Admins should look in the data base of MCBans.