Hi guys, I'm a game developer and this issue has come up on our game whilst going through testing :/
From what I can tell it's EVERY Windows 7 rig with two monitors. I've managed to replicate it in the office and the only work arounds I can see is to set the main monitor to the games native screen resolution or unplug the second monitor or run the game windowed. It appears that while 7 is running two monitors it won't let applications change one of the monitors resolutions.
So I have some questions for those whose dual monitor rigs are/aren't working;
If your dual monitors are working with full screen games:
What games are they working on? (extra brownie points if you can show me a demo that works so we don't have to pay for it!)
Is that game running in the same resolution as your desktop?
If it's the same resolution, change your main display to a different one, does it still work?
If it changes the resolution, does it change the resolution for both monitors (use a desktop image, it will change size if the resolution changes)?
Does it switch the second monitor off while playing the game?
Anything else you feel noteworthy?
If your dual monitors aren't working with full screen games:
What games have you tried?
Have you tried changing your main display resolution to the game resolution?
Have you tried unplugging the second monitor?
Have you tried anything else that made it work?
I'd really appreciate your help, it looks like lots of people are having this issue with games that were created pre-windows7 and there isn't much info on the issue. The workarounds I have mentioned do work however.