I've installed this game on 3 different Mac's.. 2 MBP and an iMac. no screen issues on any of them
That exactly were you trying to do that caused the problem? I can only think that you choose a lower resolution, like 1024 or something?
Unfortunately, on Mac anyway, there is now config file that ive been able to find with in the game packages which you could edit or just toss out and let the game start in default mode again.
It sort of shows a lack of UX/UI design experience that they don't have an escape function in case this sort of thing happens. I mean they do ask you to verify the setting you select in choosing resolution, but it doesn't take the main lobby into consideration I guess.