Yes, doing a fresh install may help.
@rjcalifornia: It points to his hosters default 404, that's because his path is wrong. if you visit http://aviate.tk/ourcatranaway/wow/wow/cache/css/default/elgg.1400601290.css there is his cached file.
So like I said changing flight-gear-box in the path to ourcatranaway/wow/wow will fix it.
I reinstalled it twice but its the same. Thanks for your help everybody, I'll try something else.
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