Maximum resolution on GT640 with a Dell 2560x1080 display

Anyone an idea if this is supported. When looking at the GT specs is should work however the GT doesn’t allow me to set this resolution.

Version info:
Linux monster 3.8.13-100.fc17.x86_64 #1 SMP Mon May 13 13:36:17 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

nvidia-settings: version 319.23 (buildmeister@swio-display-x86-rhel47-11) Thu May 16 20:17:05 PDT 2013

It is connected via the HDMI port and the Xserver config tool correctly identifies the attached monitor and shows indeed the 2560x1080 on the “Information” tab of the GPU DFP-0.

Any feedback is highly appreciated.