Created attachment 31322 [details]
A screenshot of the top right of the desktop showing the position of the truncation

I am getting odd behavior on the right hand side of my
dual monitor desktop, with acceleration enabled, but not when it is disabled.

I have a Radeon X300 in a Thinkpad T43 laptop, running default
resolution on the LCD (left), VGA (right) of 1400x1050, 1920x1080
respectively.

On one occasion this involved a scrambled screen on the right side of
the external monitor; I cannot reproduce this.

It always involves lost characters on emacs GTK screens (graphic attached).  On the graphic you can see the left hand emacs window showing the full text, and the right-hand window mainly blank, being truncated at a set position on the screen.  The position of truncation appears to be at x pixel 2640.  If I move the emacs window left or right, the characters are truncated at the same place on the screen. 

I don't get this problem with the emacs-x11 (v22) build.   The same
GTK build of emacs works without problem on an dual monitory nvidia setup on a
desktop elsewhere.

I have a Radeon X300 in a Thinkpad T43 laptop, running default
resolution on the LCD (left), VGA (right) of 1400x1050, 1920x1080
respectively.

Option "NoAccel" "on" resolves this problem but gives very slow
graphics performance.

Switching the LCD to be right of the VGA results in the problem
switching to the right side of the LCD.

lspci -v ->

01:00.0 VGA compatible controller: ATI Technologies Inc M22 [Mobility
Radeon X300]
       Subsystem: IBM Device 056e

I'm running a Karmic Koala fresh install.  I can't see any errors in
the xorg log.

xorg.conf is:

Section "Screen"
	Identifier	"Configured Screen Device"
	Device	"Configured Video Device"
	SubSection "Display"
		Virtual	3320 1080
	EndSubSection
EndSection

Section "Device"
    Identifier	"Configured Video Device"
    Driver "radeon"
EndSection