Ally, we've actually seen this error many times. Basically, there is a glitch in the system that loses nicks every once in a while. It will not be fixed until RoboOp completely re-starts the entire server. You have our permission to make a new nick name, something similar to your current one (I would suggest Ally27 or something like that) without the fee. Then it's up to you to continue trying to log in with the other one, but Robo tries not to re-start the server often, only every few months if he can help it, so we do not know when it may be fixed.