I'm running Jaunty

I have two identical 1280x1024 (max) flatscreens that, until a recent update, were working perfectly in dual setup. System>Preferences>Display showed the two monitors, and merged them to a virtual display of 2560x1024

However now the display manager seems to think my second screen is a widescreen, and no longer has the 1280x1024 option, but instead has a 16:9 option of 1360x768 (and below that: a 4:3 option of 1152x654).

When I try doing:
xrandr --output DVI-0 --mode 1280x1024
it responds with:
xrandr: cannot find mode 1280x1024
(DVI-0 is the second screen)

How can I fix this? any help would be appreciated.

# xorg.conf (X.Org 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 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.
# Note that some configuration settings that could be done previously
# in this file, now are automatically configured by the server and settings
# here are ignored.
# 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 "Monitor"
	Identifier	"Configured Monitor"

Section "Screen"
	Identifier	"Default Screen"
	Monitor		"Configured Monitor"
	Device		"Configured Video Device"
	SubSection "Display"
		Virtual	2640 1024

Section "Device"
	Identifier	"Configured Video Device"