Suddenly signoff

[Sergio]

Dear list,
I have a problem with kubuntu since I installed 10.10.
Randomly, the session crashes and I return to signon screen.
This to happen with all the users of system.
I try to install the last version of kernel from ppa and also I have 
activated xorg-edgers ppa repository to have the last driver of my ati 
video card.
Also I changed apport flag in /etc/default to have bug report, but when 
it happen nothing is detected.
All these tries went bad and I am continuing to have this big problem 
because I lost all my work when this one happen.
What I could try?
Which type informations are useful l to understand what is happening?
Excuse me about my poor english.
Thanks in advance.
Sergio bh

Kubuntu 10.10 64bit
Ati X1250 video card

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