[gutsy] X crashes when 2nd monitor is attached to Notebook

I now removed the xorg.conf and the internal screen works. The external mirrors the internal and I cannot change this through the gui because I do not have "sufficiant rights" (this is what the gui tells me).

Another thing is that the monitor buttons for changing display on my M6N lead to as system crash when I press them.

Make sure you use the latest ati driver, see https://wiki.ubuntu.com/XorgOnTheEdge
Try xrandr to configure the two screens, see http://www.intellinuxgraphics.org/dualhead.html
What gui do you use to change mirror settings?
Please attach /var/log/Xorg.0.log

So this helped a little.
I installed the ati-version from your link and some most of the graphic glitches on the external are gone, but this is what I get with xrandr -q:
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 1280 x 1200
VGA-0 connected 1280x1024+0+0 (normal left inverted right) 338mm x 270mm
   1280x1024 60.0*+ 75.0 59.9
   1152x864 75.0
   1024x768 74.9 75.1 60.0
   832x624 74.6
   800x600 75.0 74.9 60.3
   640x480 75.0 74.8 60.0
   720x400 70.1
LVDS connected 1280x800+0+0 (normal left inverted right) 0mm x 0mm
   1280x800 60.0*+ 60.0
   1280x768 60.0
   1024x768 60.0
   800x600 60.3
   640x480 59.9
S-video disconnected (normal left inverted right)

Now I cannot put the external as a big desktop because the maximum size is too small and after some time like 30 min the system froze completely

Did you set a larger "Virtual" size in xorg.conf?

No because if I use a xorg.conf the external will not run at all.
Iattached my xorg.conf and here is the output of xrandr -q with this config:
Screen 0: minimum 320 x 200, current 1600 x 1200, maximum 1920 x 1440
VGA-0 connected 1600x1200+0+0 (normal left inverted right) 338mm x 270mm
   1920x1440@60 60.0
   1600x1200@60 60.0*
   640x480@60 60.0
   640x480 60.0
LVDS connected 1280x800+0+0 (normal left inverted right) 0mm x 0mm
   1280x800 60.0*+ 60.0
   1280x768 60.0
   1024x768 60.0
   800x600 60.3
   640x480 59.9
S-video disconnected (normal left inverted right)

Yes, that xorg.conf will not work. Try making a new one by running "sudo dpkg-reconfigure -fnoninteractive xserver-xorg" in a console. Then add the Virtual option.

Invalidating xorg bug since it's already filed against -ati

Ok adjusted the xorg.conf and know this works.
One issue though everytime the external is not plugged in after stating the laptop X uses another Windowmanager and has some problems with my keyboardlayout and links on my desktop. But if the external is there then I think metacity starts.

Ohh and how do I make this monitor setting permanent so everytime I have the external on it is left of the internal one?

Can you please attach both Xorg.0.log and .xsession-errors from when the external is not plugged in and you get another window manager?

Ok after today update there is no other windowmanager in use anymore. Everything works now like a charmexcept that the external is always in clone mode after restart. Is the only option to use a static layout using the xorg.conf?
And I think the other windowmanager was compiz which will not run with both monitors because of this:

Checking for Xgl: not present.
Detected PCI ID for VGA: 01:00.0 0300: 1002:4e50 (prog-if 00 [VGA])
Checking for texture_from_pixmap: not present.
Trying again with indirect rendering:
Checking for texture_from_pixmap: present.
Checking for non power of two support: present.
Checking for Composite extension: present.
Comparing resolution (2560x1024) to maximum 3D texture size (2048): Failed.
aborting and using fallback: /usr/bin/metacity

Thanks. For a static configuration, see the how-to above.