Un g-line es un ban a la ip. A lo mejor escribiste mucho (flood), hiciste spam, o practicaste algún ejercicio maléfico por esas redes de Dios

xDD Creo que en menos de 24h debería quitársete.
Editado: Acabo de sacar esto de la web oficial:
If you're trying to connect to QuakeNet and the server tells you that you have been K-lined or G-lined it means that you have been banned from QuakeNet, and the reason for that ban is *ALWAYS* sent out right after the server tells you that you are banned. Some scripts, bots and bouncers hide this reason, but the reason is always sent. It's really up to your client/script/whatever if you ever see it or not.
The difference between a G-line and a K-line is that a G-line is network-wide and a K-line is for one server. So if you're K-lined, you can use some other server to connect to QuakeNet.
Please don't join #help asking for reasons or expiry times as they won't provide you with that info anyway.
Quiere decir que estás baneado de toda la red de QuakeNet y que en el momento del ban debieron mandarte la razón (búscala en logs o algo). El tiempo de expiración del ban lo ponen ellos, así que toca esperar
