[falko]

Can you replace the Monitor section with this one?

Section "Monitor"
        Identifier        "Generic Monitor"
        Option                "DPMS"
        HorizSync        28-51
        VertRefresh        43-60
        DisplaySize    270    203    # 1024x768 96dpi
#       DisplaySize    338    254    # 1280x960 96dpi
#       DisplaySize    338    270    # 1280x1024 96dpi
#       DisplaySize    370    277    # 1400x1050 96dpi
#       DisplaySize    423    370    # 1600x1400 96dpi
EndSection

Please make sure you uncomment the desired screen resolution (of course, your monitor and graphics card must support it).