Black bars on each side of the screen

I have black bars on each side of the client itself, not my actionbars. Resolution in the client isn't coded properly (it's set to "custom" and cannot be changed), and neither is windowed mode. Whenever I try to change to windowed mode, the game simply crashes. I'm playing on a Mac through Wine if that helps. Haven't had this problem on any of the other expansions/clients before because I can simply just change the resolution in the client. Anyone know of a fix? I have tried to download the Cataclysm client from other servers as well, doesn't work.