Well, I did another fantastico install first, and got wordpress working, and all was looking good. But I still encounter the same problem.
I think I may have pinpointed the problem. Well sort of.
I'm changing one option at a time to see which is the issue and the error reappears after typing in the Forum Relative Path. I've tried forums, /forums, /home/ggnet/gamerstyle/forums (which it clearly isn't that as it doens't even load, just an error message).
Edit, problem solved

. I had some sleep today lol

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The gxbox hack I had, was in the quick links menu, but if it's disabled it works

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Now to finish testing though now I've got that sorted