There is an issue if the "run steam when computer starts" is enabled and window manager switching.

Steps to reproduce:

1/ Enable "run Steam when my computer starts"
2/ Reboot

• system will start
• Steam will start
• everything is OK

3/ Log out from your system
4/ On a login screen choose another window manager
5/ Log in to your system
6/ Nothing happens

• Actually, Steam will start, but won't open any window. If I look in to the System Monitor, I can see Steam process with ~160MB in memory and waiting channel "futex_wait_queue_me".
• If I try to start Steam, I get this message:
  mattyy1hp@mattyy1hp-laptop ~ $ steam
  Running Steam on linuxmint 13 64-bit
  STEAM_RUNTIME is enabled automatically
  mattyy1hp@mattyy1hp-laptop ~ $
• I have to kill the Steam process. But if I do it and try to start it again, Steam says "could not connect to the Steam network".

Btw. of course, my internet connection is enabled all the time, I has also verified it by "ping" command.

My system specs:

Processor Information:
Vendor: AuthenticAMD
Speed: 1400 Mhz
4 logical processors
4 physical processors
HyperThreading: Unsupported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Supported
SSE4a: Supported
SSE41: Unsupported
SSE42: Unsupported

Network Information:
Network Speed:

Operating System Version:
Linux Mint 13 Maya (64 bit)
Kernel Name: Linux
Kernel Version: 3.6.5-030605-generic
X Server vendor: The X.Org Foundation
X Server release: 11103000

Video Card:
Driver: ATI Technologies Inc. AMD Radeon HD 6520G

Driver Version:  4.2.12002 Compatibility Profile Context 9.012
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 59 Hz
VendorID:  0x1002
DeviceID:  0x6760
Number of Monitors:  1
Number of Logical Video Cards:  2
Primary Display Resolution:  1366 x 768
Desktop Resolution: 1366 x 768
Primary Display Size: 13.54" x 7.60"  (15.51" diag)
                                        34.4cm x 19.3cm  (39.4cm diag)
Primary VRAM Not Detected

Sound card:
Audio device: ATI R6xx HDMI

Memory:
RAM: 3418 Mb

Miscellaneous:
UI Language: English
LANG: en_US.UTF-8
Microphone: Not set
Total Hard Disk Space Available: 581188 Mb
Largest Free Hard Disk Block: 153309 Mb

Installed software:

Recent Failure Reports: