Hi, I've a Compaq nw8440, similar to fangorious, with a ATI FireGL card. Also I've a similar problem, I've only one wide screen resolution available (1600 x 1050), too small for me. 
I changed the xorg.xml a few times, adding new resolutions but neither appears in "screen resolution" menu.
I've Ubuntu 7.10, with the ATI restricted driver.

Another strange behavior, the combo gives me this options:
1680 x 1050
1280 x 1024
1152 x 864
1024 x 768
600 x 600
640 x 480

And the first three are not present in the xorg.xml


# /etc/X11/xorg.conf (xorg X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf(5) manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
#   sudo dpkg-reconfigure -phigh xserver-xorg

Section "ServerLayout"
	Identifier     "Default Layout"
	Screen      0  "aticonfig-Screen[0]" 0 0
	InputDevice    "Generic Keyboard"
	InputDevice    "Configured Mouse"
	InputDevice    "stylus" "SendCoreEvents"
	InputDevice    "cursor" "SendCoreEvents"
	InputDevice    "eraser" "SendCoreEvents"
	InputDevice    "Synaptics Touchpad"
EndSection

Section "Files"

	# path to defoma fonts
	FontPath     "/usr/share/fonts/X11/misc"
	FontPath     "/usr/share/fonts/X11/cyrillic"
	FontPath     "/usr/share/fonts/X11/100dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/75dpi/:unscaled"
	FontPath     "/usr/share/fonts/X11/Type1"
	FontPath     "/usr/share/fonts/X11/100dpi"
	FontPath     "/usr/share/fonts/X11/75dpi"
	FontPath     "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
EndSection

Section "Module"
	Load  "i2c"
	Load  "bitmap"
	Load  "ddc"
	Load  "dri"
	Load  "extmod"
	Load  "freetype"
	Load  "glx"
	Load  "int10"
	Load  "vbe"
EndSection

Section "InputDevice"
	Identifier  "Generic Keyboard"
	Driver      "kbd"
	Option	    "CoreKeyboard"
	Option	    "XkbRules" "xorg"
	Option	    "XkbModel" "pc105"
	Option	    "XkbLayout" "latam"
EndSection

Section "InputDevice"
	Identifier  "Configured Mouse"
	Driver      "mouse"
	Option	    "CorePointer"
	Option	    "Device" "/dev/input/mice"
	Option	    "Protocol" "ImPS/2"
	Option	    "ZAxisMapping" "4 5"
	Option	    "Emulate3Buttons" "true"
EndSection

Section "InputDevice"
	Identifier  "Synaptics Touchpad"
	Driver      "synaptics"
	Option	    "SendCoreEvents" "true"
	Option	    "Device" "/dev/psaux"
	Option	    "Protocol" "auto-dev"
	Option	    "HorizScrollDelta" "0"
EndSection

Section "InputDevice"
	Identifier  "stylus"
	Driver      "wacom"
	Option	    "Device" "/dev/input/wacom"
	Option	    "Type" "stylus"
	Option	    "ForceDevice" "ISDV4"# Tablet PC ONLY
EndSection

Section "InputDevice"
	Identifier  "eraser"
	Driver      "wacom"
	Option	    "Device" "/dev/input/wacom"
	Option	    "Type" "eraser"
	Option	    "ForceDevice" "ISDV4"# Tablet PC ONLY
EndSection

Section "InputDevice"
	Identifier  "cursor"
	Driver      "wacom"
	Option	    "Device" "/dev/input/wacom"
	Option	    "Type" "cursor"
	Option	    "ForceDevice" "ISDV4"# Tablet PC ONLY
EndSection

Section "Monitor"
	Identifier   "Generic Monitor"
	Option	    "DPMS"
EndSection

Section "Monitor"
	Identifier   "aticonfig-Monitor[0]"
	Option	    "VendorName" "ATI Proprietary Driver"
	Option	    "ModelName" "Generic Autodetecting Monitor"
	Option	    "DPMS" "true"
EndSection

Section "Device"
	Identifier  "Generic Video Card"
	Driver      "fglrx"
	BusID       "PCI:1:0:0"
EndSection

Section "Device"
	Identifier  "aticonfig-Device[0]"
	Driver      "fglrx"
EndSection

Section "Screen"
	Identifier "Default Screen"
	Device     "Generic Video Card"
	Monitor    "Generic Monitor"
	DefaultDepth     24
	SubSection "Display"
		Depth     1
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
	SubSection "Display"
		Depth     4
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
	SubSection "Display"
		Depth     8
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
	SubSection "Display"
		Depth     15
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
	SubSection "Display"
		Depth     16
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
	SubSection "Display"
		Depth     24
		Modes    "1024x768" "800x600" "640x480"
	EndSubSection
EndSection

Section "Screen"
	Identifier "aticonfig-Screen[0]"
	Device     "aticonfig-Device[0]"
	Monitor    "aticonfig-Monitor[0]"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Depth     24
		Modes    "1280x768"
	EndSubSection
EndSection

Section "DRI"
	Mode         0666
EndSection

Section "Extensions"
	Option	    "Composite" "1"
EndSection