yes it is possible to ban your mac-adress.
i had the same problem with xiu-server.
you can change your mac-adress with SMAC, a little programm for this.
just google for SMAC 2.0.
download and change your mac and the ban should end.
worked fine for me XD
btw SMAC 2.0.5 is now not freeware anymore, so you should find any way to "buy" it for full service ^^ the trial version makes you only able to change your mac to only ONE new mac...
btw² no matter what you do with smac and no matter it tells you... the change of the mac will only take effect after YOU disactivate/reactivate your network-card by yourself. (dunno why, but the program tells you, that it is doing this, but you have to do it yourself after that)
gl