Wow: Cross faction guild not working

Got a problem to be invite in a guild of opposite faction, the gm that i got in my friend list got this message: “You can’t invite players from the opposing faction”, i’ve already try to delete cache and interface folders, also try to be adding by another member still the same problem, if someone got a solution about it.

Why not ask in the WoW forums ? (no, the forums here aren’t it)