A gline is a global network ban, meaning you are banned from all servers on that network. This is usually done rarely and on most networks only after a vote from several servers. Most networks will gline for only a limited period of time (while a kline -- ban for only one server -- can be anywhere from a minute to until hell freezes over, depending on the discretion of the oper setting the kline).
Clearing cookies and cache won't help you. The message you received indicates misbehavior or other violation of server/network policies. That is something that needs to be discussed, usually via email, with the network authorities.
Last edited by Handle_With_Care; 27/02/11 12:45 AM.