I have a Radeon 5750 GPU outputting to three monitors (1 DisplayPort, 1 DVI, 1 HDMI). For a while now, I had a 1920x1080 left monitor, 1680x1050 right monitor and a TV at 1920x1080 mounted above and in between these two monitors. So it looked like this (don't have privileges to add images yet):
  
I finally bought a new right monitor to match the 1920x1080 resolution of my TV and left monitor. When I plugged it in, and rebooted, the structure became linear, such as this:
The problem is every time I try to position the displays how I originally had it, Windows will try to do it, flicker, and immediately go back to some linear structure. It gets weirder. If I make device  have a resolution of 1680x1050, and then try to position them, the displays are correctly positioned without any problem. Obviously this is not what I want, as the point of getting a matching pair of monitors was to have the same resolution on all my outputs.
My drivers are all up-to-date and Catalyst Control Center is up-to-date as well. I am running Windows 7 x64. Any idea what could be causing the issue? Thanks!
I can also lower device  or device  resolution and it correctly positions without a problem. If I change all the resolutions to 1680x1050, Windows tries, flickers and reverts. Could there be something weird with having all three devices set to the same resolution that is not allowing me to position them correctly?