Normally I would say you misbehaved in some way and got banned from the channel, but then I'd think the join error message would be "cannot join, you are banned (from this channel)", instead it says "channel is banned" so it sounds like it's got to be something _you_ did internally, not something the channel admins or the piggies did to you. Even if you uninstalled it, may apps don't clear out their registry entries automatically and it might have been storing your ignore / ban list there still. I know a while back they banned a bunch of people who were hanging out in Yue-bing's channel (she is basically a rival of the piggies) so maybe you got caught up in that, but from the error message you get it really sounds like it's something more on your side.
If you did get caught up in a ban, if you feel it was unjustified you can call up the piggy over Skype (see the instructions on the site) and try to bribe him with gifts, or you can challenge him to a game of shoji, but he won't play with a handicap even if you are a newb so don't think he's easy to beat... good luck if this is the case...
