Странно, однако. У меня видеокарта nVidia GeForce 8800GTS и 22" монитор с разрешением 1680х1050. В kde4 никаких проблем с разрешением монитора никогда не возникало. Драйвер для видеокарты ставил из репозитория. Вот мой xorg.conf:
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "us,ru(winkeys),ua(winkeys)"
Option "XkbVariant" ","
Option "XkbOptions" "grp:ctrl_shift_toggle,lv3:ralt_switch"
EndSection
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
EndSection
Section "Device"
Identifier "Configured Video Device"
Driver "nvidia"
Option "NoLogo" "True"
EndSection
Section "Monitor"
Identifier "Configured Monitor"
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
Defaultdepth 24
EndSection
Section "ServerLayout"
Identifier "Default Layout"
screen "Default Screen"
EndSection
Section "Module"
Load "glx"
EndSection