Bug 722546

Description of problem:
it happened two times after today updates that I have complete system freeze on my system.
first time after few minutes after boot. Another time after about 7 hours...
I'm going to attach latest today updates.
Both times I was using evolution:
- mouse scrolling through inbox folder items
- mouse click between sent items and inbox folder
I'm using evolution-mapi to connect to exchange 2007

I tipically have many applications open and I'm not always in evolution window,
So first attempt to bugzilla against evolution, but then I changed to kernel due to complete freeze...
After freeze I have no mouse pointer movement indication, no network reachability
let me know how to debug this, please... 

Version-Release number of selected component (if applicable):
2.6.38.8-35.fc15.x86_64

How reproducible:
random

Steps to Reproduce:
1. boot system
2. open some applications (eg evolution, firefox, virt-manager, gnome-terminal)
3. work in the system
  
Actual results:
after few minutes o few hours I get complete freeze

Expected results:
normal behaviour

Additional info:
I have been using F15 since RC3 on this system and didn't get any freeze like this...
It has begun happening right today.
I admit information is quite vague... and could also be related to something else (such as hw dying, ecc)

Some details about the system
Dell XPS M1330 laptop where default nouveau driver is installed
I got the first freeze at about 09:50 and this is the content of /var/log/messages:
Jul 15 09:49:51 ope46 dbus: [system] Activating service name='org.freedesktop.PackageKit' (using servicehelper)
Jul 15 09:49:51 ope46 dbus: [system] Successfully activated service 'org.freedesktop.PackageKit'
Jul 15 09:53:19 ope46 kernel: imklog 5.8.2, log source = /proc/kmsg started.
Jul 15 09:53:19 ope46 rsyslogd: [origin software="rsyslogd" swVersion="5.8.2" x-pid="929" x-info="http://www.rsyslog.
com"] start


At the second freeze (at about 17:24):
Jul 15 16:58:58 ope46 dbus: [system] Successfully activated service 'org.freedesktop.PackageKit'
Jul 15 17:04:25 ope46 pulseaudio[1805]: ratelimit.c: 491 events suppressed
Jul 15 17:26:25 ope46 kernel: imklog 5.8.2, log source = /proc/kmsg started.
Jul 15 17:26:25 ope46 rsyslogd: [origin software="rsyslogd" swVersion="5.8.2" x-pid="904" x-info="http://www.rsyslog.com"] st
art
Jul 15 17:26:25 ope46 kernel: [    0.000000] Initializing cgroup subsys cpuset

Any way to use any debug, such as Ctrl+Alt+PrntScr to debug...?