Thanks for doing this! I'm sure many people experiencing this problem would love to find this in a Google result rather than having to trudge around forever, finally deciding to sign up and ask what's wrong then waiting a few days for a good answer.
I should know - I've had it a lot with other problems.

I would expect that something like this would occur. WoG was probably made without expecting people to go with an extended desktop, so a bug is only natural. Glad that you're content with your simple solution (I don't think there's any other fix anyway ).

Alternately, hit Alt+Enter while it's flipping out. This will switch the game to windowed mode. It's a common shortcut for some other full-screen programs and games. The downside is it'll be in a little window, which kinda stinks if you usually run at high resolution, but at least you won't have to change your display configuration.

Would love to see this issue fixed though. Multiple monitor setups are hardly unusual.

Alt+Enter is known. By the way, windowed mode doesn't take off any pixels, it shows exactly how large you're viewing the game. If it's smaller, then the game must have been stretched for fullscreen.