different resolutions for second monitor on imac?

[buckandphollux]

Hi, has anyone got a suggestion for the following problem:
I have 2 imacs and a mac mini.

LEFTIE is a 7.1 with a ATI Radeon HD2600 with 256MB RAM, and
RIGHTIE is a 8.1 with NVIDIA GeFORCE 8800 GS with 512MB RAM
Mac mini is brand new.

I have just purchased 3 x LG L246WHX monitors.

NO matter which one I connect via DVI - HDMI to RIGHTIE the max resolution on the second monitor is 1920 x 1080 although RIGHTIE is still 1920 x 1200, but all of the monitors work just fine on LEFTIE at 1920 x 1200 and on the mac mini. Any ideas?

Thanks in advance.

 

[Hellhammer]

Try DVI cable if you have one. If it doesn't help, I would call to Apple or LG

 

[indg]

you may need a third-party app to set a custom resolution. try one of these...
SwitchResX: http://www.madrau.com/SRX3/index.html
DisplayConfigX: http://www.3dexpress.de/

i used displayconfigx on my macbook pro to get the native resolution on my vizio lcd (1280x768) that my ATI video card supports, but os x didn't offer as one of the resolutions for the display.