Created attachment 4944 
xorg.conf as in use of today

Hello,
I am not too sure wether this is the correct area to address the below following issue, but I did notfind any better location yet.

Currently I am using two LCD-Monitors with physical resolutions of 1280x1024 each and an virtual resolution of 1600x1200 on each resulting in a twinview screen of 3200x1200.
My box runs an uptodate debian-sid (siduction),currently with kernel 3.8-1, nvidia-driver 313.18 and X.Org: 1.12.4.

Since the nvdia-driver series 3xx.xx came out I have the problem with xfce (and only with xfce) that the vritual resolution/panning area is scrambled/showing garbage when starting xfce. At earlier times I could go back to the 29x.ssdrivers from nvidia but nowadays those donot run with the newer kernels and newer X anymore.

The panels, originally placed at the bottom of the screen, are being somehow raised up to fit within the phys.resolution of 1280x1024.

When starting the display manager (kdm currently) everything is fine and running as expected. Only when starting xfce this strange behaviour comes up and stays until I sign off and restart the xaserver and display manager.
Then erverything is fine again until I restart xfce.

This occured with xfce-versions 4.8 and also with 4.10. Other desktop-enviroments (razorqt, kde, icwm) donot have this problem at all.
The problem is notbound on this machine, an other (similar/nearly identical) box shows the same effects when using virtual resolution/panning with xfce.

I also contacted nvidia support on that and the (what else :-)) blamed xfce on that. Unfortunately they might be right this time :-(

It looks to me as xfce is resetting the screen to some pre-configured sizes but isn't able to handle those virtual resolutions/panning any more within actual xorg/nvidia-drivers as it could before.
I have attached copy ofthe current xor.conf in use.

Any idea or solution what could be wrong or how this problem could be solved ?

regards

Reiner