Cannot get 1366x768 screen above 1024x768, & man xrandr inconsistancy

[Brett Mahar <brett.mahar@gmail.com>]

Hi,
I have an emachine ET1300-02 computer, which came with emachine
1366x768 monitor. MCP61 motherboard with Nvidia GeForce G100 graphical
chipset.
When installing Debian 5 or 5.05, it come sup with a floating "output
not supported" on the screen.
By pressing ctrl+alt++ I can get to a visible screen, or by logging
into single user mode I can edit xorg.conf to get to a default screen
size of 1024x768, so screen is viewable on reboot. However, I cannot
get above this resolution. This only happens with Debian, with the
same hardware on OpenBSD, Fedora 12 or 13, Ubuntu 9.10 or 10.04, I can
get correct resolution no problem.

I have tried deleting completely the xorg.conf file, also have editied
it using output from cvt to set:
Modeline "1368x768_60.00" 85.25  1368 1440 1576 1784  768 771 781 798
-hsync +vsync
Also have added new modes "1368x768" "1366x768" "1368x768_60.00" to no effect.

Command xrandr gives the output:
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 768
default connected
   1024x768        0.0
   800x600        61.0
   640x480        60.0
   640x400         0.0
   320x400         0.0
   320x240         0.0
   320x200         0.0

As root I run the script:
su -c xrandr
xrandr --newmode "1368x768" 60  1368 1440 1576 1784  768 771 781 798
-hsync +vsync
xrandr --addmode VGA 1368x768
xrandr --output VGA --preferred 1368x768 --fb 1368x768 --fbmm 1368x768
--mode 1368x768
xrandr --size 1368x768
#and all conceivable variations of the above!!!!

If I type command xrandr again:
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 768
default connected
   1024x768        0.0
   800x600        61.0
   640x480        60.0
   640x400         0.0
   320x400         0.0
   320x240         0.0
   320x200         0.0
  1368x768 (0x4e)   60.0MHz
        h: width  1368 start 1440 end 1576 total 1784 skew    0 clock   33.6KHz
        v: height  768 start  771 end  781 total  798           clock   42.1Hz

Somehow I am not able to get the "maximum" above 1024x768. Anyone have
any ideas where I should be looking?
By the way, xrandr manual page says: "If invoked without any option,
it will dump the state of  the  outputs, showing  the existing modes
for each of them, with a ’+’ after the preferred mode and a ’*’ after
the current mode."
As you can see from outputs above, there is no '+' or '*' when I use
this command.

Cheers, Brett.