The issue is as the title says. All i need to do to reproduce the crash is try to open big picture mode, crashes everytime.
Command line output:
shawn@shawn-desktop:~/.steam/steam$ '/home/shawn/.steam/steam/steam.sh'
Running Steam on ubuntu 12.04 64-bit
STEAM_RUNTIME is enabled automatically
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Looks like steam didn't shutdown cleanly, scheduling immediate update check
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
unlinked 0 orphaned pipes
removing stale semaphore last operated on by process 5391 with name 0eBlobRegistryMutex_07D9C081F8835AA6F302C638C45A3360
removing stale semaphore last operated on by process 5391 with name 0eBlobRegistrySignal_07D9C081F8835AA6F302C638C45A3360
removing stale semaphore last operated on by process 5391 with name 0emSteamEngineInstance
removing stale semaphore last operated on by process 5391 with name 0eSteamEngineLock
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
[0210/131305:WARNING:proxy_service.cc(646)] PAC support disabled because there is no system implementation
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Generating new string page texture 2: 48x256, total string texture memory is 49.15 KB
Generating new string page texture 3: 384x256, total string texture memory is 442.37 KB
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
`menu_proxy_module_load': /home/shawn/.steam/steam/ubuntu12_32/steam: undefined symbol: menu_proxy_module_load

(steam:5635): Gtk-WARNING **: Failed to load type module: (null)

Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
Adding license for package 0
Adding license for package 7
Adding license for package 37
Adding license for package 16222
roaming config store loaded successfully - 601 bytes.
migrating temporary roaming config store
ExecCommandLine: "/home/shawn/.local/share/Steam/ubuntu12_32/steam"
Generating new string page texture 69: 128x256, total string texture memory is 573.44 KB
Generating new string page texture 70: 128x256, total string texture memory is 131.07 KB
Generating new string page texture 71: 256x256, total string texture memory is 835.58 KB
Generating new string page texture 72: 64x256, total string texture memory is 901.12 KB
Generating new string page texture 73: 32x256, total string texture memory is 933.89 KB
removing stale semaphore last operated on by process 5391 with name 0eBlobRegistryMutex_A3706368A660525D8AD7F51167092E57
removing stale semaphore last operated on by process 5391 with name 0eBlobRegistrySignal_A3706368A660525D8AD7F51167092E57
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
System startup time: 13.76 seconds
Running Steam on ubuntu 12.04 64-bit
STEAM_RUNTIME has been set by the user to: /home/shawn/.steam/steam/ubuntu12_32/steam-runtime
ExecCommandLine: "/home/shawn/.steam/root/ubuntu12_32/steam steam://open/driverhelperready"
ExecSteamURL: "steam://open/driverhelperready"
Generating new string page texture 83: 256x256, total string texture memory is 393.22 KB
Generating new string page texture 88: 128x256, total string texture memory is 1.06 MB
Generating new string page texture 115: 512x256, total string texture memory is 1.59 MB
Generating new string page texture 116: 2048x256, total string texture memory is 3.69 MB
Generating new string page texture 117: 256x256, total string texture memory is 3.95 MB
Generating new string page texture 118: 128x256, total string texture memory is 4.08 MB
Generating new string page texture 119: 1024x256, total string texture memory is 5.13 MB
Installing breakpad exception handler for appid(steam)/version(1360439662_client)
steam: ../../src/xcb_conn.c:180: write_vec: Assertion `!c->out.queue_len' failed.
/home/shawn/.steam/steam/steam.sh: line 561: 5635 Segmentation fault (core dumped) $STEAM_DEBUGGER "$STEAMROOT/$PLATFORM/$STEAMEXE" "$@"

System Information

Processor Information:
Vendor: AuthenticAMD
Speed: 3100 Mhz
8 logical processors
8 physical processors
HyperThreading: Unsupported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Supported
SSE41: Supported
SSE42: Supported

Network Information:
Network Speed:

Operating System Version:
Ubuntu 12.04.2 LTS (64 bit)
Kernel Name: Linux
Kernel Version: 3.2.0-37-generic
X Server vendor: The X.Org Foundation
X Server release: 11103000

Video Card:
Driver: ATI Technologies Inc. ATI Radeon HD 5700 Series

Driver Version:  4.2.12002 Compatibility Profile Context 9.012
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x1002
DeviceID:  0x68b8
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 6.30" x 3.54"  (7.20" diag)
                                        16.0cm x 9.0cm  (18.3cm diag)
Primary VRAM Not Detected

Sound card:
Audio device: Realtek ALC892

Memory:
RAM: 7915 Mb

Miscellaneous:
UI Language: English
LANG: en_CA.UTF-8
Microphone: Not set
Total Hard Disk Space Available: 930907 Mb
Largest Free Hard Disk Block: 570638 Mb

Installed software:

Recent Failure Reports: