Unable to change X resolution

[Mike Linksvayer]

Ubuntu 6.06 (upgrade from 5.10, though this didn't work on 5.10, I
just never bothered to try to fix it), Dell Inspiron 6000, i915GM
video chipset.

I'm using 915resolution to obtain 1920x1200.  In this case
System|Preferences|Screen Resolution offers me 1920x1200 and
1600x1200.  If I do not use 915resolution I only get 1600x1200.  I
actually get 1600x1200 as an option even if I do not include it in
xorg.conf.

However, my xorg.conf also specifies 1280x1024, 1024x768 and 800x600
(I want to switch to lower resolutions for external  video).  What
am I missing in order to make those resolutions available?

My xorg.conf is pasted below.  I'd be happy to provide additional
information.  I hope that I am just being stupid in which case I
apologize in advance for this. :-)

Thanks,
Mike

# /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 /etc/X11/xorg.conf manual page.
# (Type "man /etc/X11/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 "Files"
	FontPath	"/usr/share/X11/fonts/misc"
	FontPath	"/usr/share/X11/fonts/cyrillic"
	FontPath	"/usr/share/X11/fonts/100dpi/:unscaled"
	FontPath	"/usr/share/X11/fonts/75dpi/:unscaled"
	FontPath	"/usr/share/X11/fonts/Type1"
	FontPath	"/usr/share/X11/fonts/CID"
	FontPath	"/usr/share/X11/fonts/100dpi"
	FontPath	"/usr/share/X11/fonts/75dpi"
        # paths to defoma fonts
	FontPath	"/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
	FontPath	"/var/lib/defoma/x-ttcidfont-conf.d/dirs/CID"
EndSection

Section "Module"
	Load	"GLcore"
	Load	"i2c"
	Load	"bitmap"
	Load	"ddc"
	Load	"dri"
	Load	"extmod"
	Load	"freetype"
	Load	"glx"
	Load	"int10"
	Load	"type1"
	Load	"vbe"
EndSection

Section "InputDevice"
	Identifier	"Generic Keyboard"
	Driver		"kbd"
	Option		"CoreKeyboard"
	Option		"XkbRules"	"xorg"
	Option		"XkbModel"	"pc104"
	Option		"XkbLayout"	"us"
EndSection

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

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

Section "Device"
	Identifier	"Intel Corporation Intel Default Card"
	Driver		"i810"
	BusID		"PCI:0:2:0"
EndSection

Section "Modes"
	Identifier "16:10"
	# 800x600 @ 60.00 Hz (GTF) hsync: 37.32 kHz; pclk: 38.22 MHz
	Modeline "800x600"  38.22  800 832 912 1024  600 601 604 622  -HSync +Vsync
	# 1024x768 @ 60.00 Hz (GTF) hsync: 47.70 kHz; pclk: 64.11 MHz
	Modeline "1024x768"  64.11  1024 1080 1184 1344  768 769 772 795  -HSync +Vsync
	# 1280x1024 @ 60.00 Hz (GTF) hsync: 63.60 kHz; pclk: 108.88 MHz
	Modeline "1280x1024"  108.88  1280 1360 1496 1712  1024 1025 1028 1060 -HSync +Vsync
	# 1600x1200 @ 60.00 Hz (GTF) hsync: 74.52 kHz; pclk: 160.96 MHz
	Modeline "1600x1200"  160.96  1600 1704 1880 2160  1200 1201 1204 1242 -HSync +Vsync
	# 1920x1200 @ 60.00 Hz (GTF) hsync: 74.52 kHz; pclk: 193.16 MHz
	Modeline "1920x1200"  193.16  1920 2048 2256 2592  1200 1201 1204 1242 -HSync +Vsync
EndSection


Section "Monitor"
	Identifier	"Generic Monitor"
	Option		"DPMS"
	UseModes	"16:10"
EndSection


Section "Screen"
  Identifier  "Default Screen"
  Device       "Intel Corporation Intel Default Card"
  Monitor      "Generic Monitor"
  DefaultDepth 24

  Subsection "Display"
    Depth       24
    Modes       "1920x1600" "1600x1200" "1280x1024" "1024x768" "800x600"
  EndSubsection
EndSection

Section "ServerLayout"
	Identifier	"Default Layout"
	Screen		"Default Screen"
	InputDevice	"Generic Keyboard"
	InputDevice	"Configured Mouse"
	InputDevice	"Synaptics Touchpad"
EndSection

Section "DRI"
	Mode	0666
EndSection