groupmanager alone wont make your name have a prefix, you need essentials chat or some other chat plugin. and you need prefix: 'whatever' you dont have that
The error shouldn't have anything to do with Java. OpenGL is a graphics library that Minecraft uses. If there is no update to your video card then there is a chance that the video card doesn't have that feature (Most do but...). If this is the case Google the problem and try to see if someone else has the same problem.
Alt accounts means nothing whatsoever, it just means you have friends. If they ban you for having an Alt account then the server owners probably do not know how it works. If admins ask about it then just explain that you have friends that play on your IP.
I can help! PM me your skype, I used to have my own server a while ago but then it got too expensive . I am very good with GroupManager and can make the permissions in a day or so even if they are very complicated.
Change the port to 25566 to see if it fixes the problem. If you really want 25565 as the port, restart your computer and then try.
EDIT:Restart it anyways to see if it fixes it, the error means something is already running on that port, maybe you accidentally ran the server while the server was still running?
