Bad interaction between multihead display amd desktops in debian squeeze

[Mauro Condarelli <mc5686@mclink.it>]

Hi,
I am struggling to make work my new Debian Squezze installation on my workhorse.
Problem is X setup and its interaction with desktops.

I have two VGAs:
* intel embedded in my i7 CPU
* external NVidia GTX770
Each of them drives 2 monitors for a grand total of 4.

I managed to have partial victory in the sense:
I can have dual monitor using *either* intel *or* nvidia
or I can have all four, but then gnome crashes somehow ("Oh no! Something went wrong...") while X is ok.
In the "working" cases xrandr dees only the two active monitors.
I also installed Xfce which works happily with the same config where Gnome crashes, but shows only the nvidia monitors with mirroring and xrandr does not work at all.

I am now writing from Win7 (with all monitors correctly working!) and thus I have no access to actual files.

Can someone point me in the right direction, please?

Mauro