Tyrant, я сам в юниксах ещё новенький...
Попробуй в файле /etc/X11/xorg.conf дописать характеристики своего монитора. У меня вот так написано там:
Код:

Section "Monitor"
Identifier "monitor1"
VendorName "Plug'n Play"
ModelName "F700P "
HorizSync 30-98
VertRefresh 50-160
# Monitor preferred modeline (85.0 Hz vsync, 91.1 kHz hsync, ratio 5/4)
ModeLine "1280x1024" 157.5 1280 1344 1504 1728 1024 1025 1028 1072 +hsync +vsync
# TV fullscreen mode or DVD fullscreen output.
# 768x576 @ 79 Hz, 50 kHz hsync
ModeLine "768x576" 50.00 768 832 846 1000 576 590 595 630
# 768x576 @ 100 Hz, 61.6 kHz hsync
ModeLine "768x576" 63.07 768 800 960 1024 576 578 590 616
EndSection
Section "Device"
Identifier "device1"
VendorName "nVidia Corp."
BoardName "NVIDIA GeForce 6 Series"
Driver "nvidia"
Option "DPMS"
EndSection
Section "Screen"
Identifier "screen1"
Device "device1"
Monitor "monitor1"
DefaultColorDepth 24
Subsection "Display"
Depth 8
Modes "1280x1024" "1152x864" "1024x768" "832x624" "800x600" "640x480" "480x360" "320x240"
EndSubsection
Subsection "Display"
Depth 15
Modes "1280x1024" "1152x864" "1024x768" "832x624" "800x600" "640x480" "480x360" "320x240"
EndSubsection
Subsection "Display"
Depth 16
Modes "1280x1024" "1152x864" "1024x768" "832x624" "800x600" "640x480" "480x360" "320x240"
EndSubsection
Subsection "Display"
Depth 24
Modes "1280x1024" "1152x864" "1024x768" "832x624" "800x600" "640x480" "480x360" "320x240"
EndSubsection
EndSection
Там, конечно, ещё много чего написано, но к монитору не имеет отношения.