Might be an issue with what your driver is exposing. If you haven't done so already, might want to go into the control panel and such to make sure you've enabled the unsupported resolutions for your monitor (forget the exact wording but the option states something to that effect). Might need to create/test/save custom resolutions as well through the graphics card's interface as well.

Last case scenario you might be able to manually edit the config file to use the larger values. Haven't had a chance to poke around yet...but pre-patch the file was plain text with clear labels for the values.