Could you upload these crash*.dmp files and link them for the Valve devs to look through please, anywhere is fine, ubuntu one, dropbox etc.

Dump files uploaded to here: http://dl.dropbox.com/u/27017764/dumps.tgz

Installed Nvidia drivers and tested again. Still crashed, when receiving a message after closing the chat window, but dump appeared to upload successfully. New sys info:

Driver Version:  4.2.0 NVIDIA 304.64
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 59 Hz
VendorID:  0x10de
DeviceID:  0xe22
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 18.90" x 10.63"  (21.65" diag)
                                        48.0cm x 27.0cm  (55.0cm diag)
Primary Bus: PCI Express 16x
Primary VRAM: 1023 MB
Supported MSAA Modes:  2x 4x 8x 16x 

Recent Failure Reports:
Sat Mar 30 03:50:05 2013 GMT: file ''/tmp/dumps/assert_20130329205005_1.dmp'', upload no: ''HTTP response code said error''
Sat Mar 30 04:05:59 2013 GMT: file ''/tmp/dumps/crash_20130329210558_2.dmp'', upload no: ''HTTP response code said error''
Sat Mar 30 04:13:18 2013 GMT: file ''/tmp/dumps/crash_20130329211257_1.dmp'', upload no: ''HTTP response code said error''
Sat Mar 30 04:51:11 2013 GMT: file ''/tmp/dumps/assert_20130329215109_1.dmp'', upload no: ''HTTP response code said error''
Sun Mar 31 19:56:09 2013 GMT: file ''/tmp/dumps/crash_20130331125607_1.dmp'', upload yes: ''CrashID=bp-66b7ea06-5f31-4215-9e4d-89a5b2130331
''


I didn't notice, but it looks like there was a SELinux alert with a matching time-stamp! Might need to put this on an FAQ somewhere...

Here's the text of the alert details:

SELinux is preventing /home/aalpert/.local/share/Steam/ubuntu12_32/steam from using the execheap access on a process.
*****  Plugin allow_execheap (53.1 confidence) suggests  *********************
If you do not think /home/aalpert/.local/share/Steam/ubuntu12_32/steam should need to map heap memory that is both writable and executable.
Then you need to report a bug. This is a potentially dangerous access.
Do
contact your security administrator and report this issue.
*****  Plugin catchall_boolean (42.6 confidence) suggests  *******************
If you want to allow unconfined executables to make their heap memory executable.  Doing this is a really bad idea. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla
Then you must tell SELinux about this by enabling the 'selinuxuser_execheap' boolean.
You can read 'unconfined_selinux' man page for more details.
Do
setsebool -P selinuxuser_execheap 1
*****  Plugin catchall (5.76 confidence) suggests  ***************************
If you believe that steam should be allowed execheap access on processes labeled unconfined_t by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# grep steam /var/log/audit/audit.log | audit2allow -M mypol
# semodule -i mypol.pp
Additional Information:
Source Context                unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1
                              023
Target Context                unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1
                              023
Target Objects                 [ process ]
Source                        steam
Source Path                   /home/aalpert/.local/share/Steam/ubuntu12_32/steam
Port                          
Host                          localhost.localdomain
Source RPM Packages           
Target RPM Packages           
Policy RPM                    selinux-policy-3.11.1-86.fc18.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     localhost.localdomain
Platform                      Linux localhost.localdomain 3.8.4-202.fc18.x86_64
                              #1 SMP Thu Mar 21 17:02:20 UTC 2013 x86_64 x86_64
Alert Count                   1
First Seen                    2013-03-31 12:56:07 PDT
Last Seen                     2013-03-31 12:56:07 PDT
Local ID                      661b8f22-7b4d-452c-aae7-1fbe9ab33a72
Raw Audit Messages
type=AVC msg=audit(1364759767.751:324): avc:  denied  { execheap } for  pid=2969 comm="steam" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=process
type=SYSCALL msg=audit(1364759767.751:324): arch=i386 syscall=capget success=no exit=EACCES a0=d779000 a1=c000 a2=7 a3=ff809afc items=0 ppid=2878 pid=2969 auid=1000 uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 ses=1 tty=pts1 comm=steam exe=/home/aalpert/.local/share/Steam/ubuntu12_32/steam subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
Hash: steam,unconfined_t,unconfined_t,process,execheap
audit2allow
#============= unconfined_t ==============
#!!!! This avc can be allowed using the boolean 'selinuxuser_execheap'
allow unconfined_t self:process execheap;
audit2allow -R
require {
    type unconfined_t;
    class process execheap;
}
#============= unconfined_t ==============
#!!!! This avc can be allowed using the boolean 'selinuxuser_execheap'
allow unconfined_t self:process execheap;