I have this peculiar problem in F8 where the configuration tools do not let me choose a resolution higher than 800x600 even though I have selected a monitor capable of doing 1440x900. Manually hacking the xorg.conf file, putting in my monitor's H/V sync values and the desired resolution in the Screen section, I manage to get X to display at 1440x900. GDM/gnome however seem to think they are still in 800x600 resolution. This leads to the problem of having a desktop of 800x600 in a 1440x900 larger desktop. You can see in the attached picture that yumex maxed in the 800x600 desktop while xchat is maxed in the 1440x900 desktop. note also the panel bars.
--== Anything can go wrong. It's just a matter of how far wrong it will go till people think its right. ==--
--== Anything can go wrong. It's just a matter of how far wrong it will go till people think its right. ==--