Cant change resolution format in the video settings.

when ever i try change from the standart 1024x768 format and to 1600x900 widescreen then it just flashes the screen and goes back to the old resolution. this also happends for all the other wide screen settings. sometimes it crashes and a "submit a bugreport" window pops up.
Anyone that know what is wrong or so ? please help me to identify the problem and resolution thanks.
Anyone that know what is wrong or so ? please help me to identify the problem and resolution thanks.