For people experiencing troubles with setting higher resolutions:
Make sure you have latest driver for your graphics card installed. Uninstall your current graphics card first, before installing the new one.
Ati cards -
http://ati.amd.com/
Nvidia cards -
http://www.nvidia.com/Download/index.aspx?lang=en-us
Also, download and install latest driver for your monitor (you can get it on monitor manufacturer`s website). Without driver, your monitor acts as Plug & Play standart device and this may cause the problem.