I went to the Starchat IRC help channel, and another person there was also getting kicked while trying to connect via Mibbit. Another chat regular tried to get into chat via Mibbit and was blocked.
In short, the problem seems to be related to Mibbit itself. Try using other IRC clients such as KiwiIRC (which you do not need to download) for the meantime, and send an email to the address in the kick message.
I'll post again if/when I get a response to my email. The person in the help channel said that they themselves couldn't fix it, so inquiring in the #Starchat channel will likely not net a fix.
Agreeing with Lily that the problem does seem to be something to do with mibbit being blacklisted. Starchat subscribes to an outside service that provides blacklists, so the issue is with that service, not starchat.
If anyone is having trouble connecting and getting the same k-lined message and is NOT using mibbit, post and let us know?