You may have to force the system to use an xorg.conf file and define your parameters there... A few years back, Xorg went to an autodetect system, ... Fixed some things, broke others.
What you might have to do is a stop service on your login manager, and then do a;
sudo dpkg-reconfigure xserver-xorg
That should generate an xorg.conf in /etc/X11/ & from there you may have to edit it (if you're editing at command line, I recommend installing nano,... much better/easier than vi). You should take a look at sample xorg.conf files for your chipset, and the resolution you're looking to display at...
And with TVs,... inevitably it's EDID getting in the way... TVs often do not even report native resolution over their vga ports (if they have one). Many have a "simulated" 1080p resolution, even while they have a native 1360x768 or 1366x768 resolution.
Last edited by JaseP; 10-15-2012 at 01:26 PM.