Garry's Mod fails to start on Kubuntu 13.04

Hi GMod Community,

Every time I try to run Garry’s Mod on Kubuntu 13.04 (64bit) it exit with this Error:
Engine Error - Could not load library client

I allready followed every step on this Page and after this failed I removed the Garry’s Mod folder “/home/robin/.steam/steam/SteamApps/common/GarrysMod/” (aka. Totally Clean). However, It didn’t help me…
Has somebody experienced a similar error and maybe found a solution? :wink:

System Information:

Processor Information:
    Vendor:  GenuineIntel
    Speed: 3100 Mhz
    4 logical processors
    2 physical processors
    HyperThreading:  Supported
    FCMOV:  Supported
    SSE2:  Supported
    SSE3:  Supported
    SSSE3:  Supported
    SSE4a:  Unsupported
    SSE41:  Supported
    SSE42:  Supported
Network Information:
    Network Speed:  
Operating System Version:
    Ubuntu 13.04 (64 bit)
    Kernel Name:  Linux
    Kernel Version:  3.8.0-25-generic
    X Server Vendor:  The X.Org Foundation
    X Server Release:  11303000
    X Window Manager:  KWin
    Steam Runtime Version:  steam-runtime-release-i386_2013-05-08
Video Card:
    Driver:  ATI Technologies Inc. AMD Radeon HD 6670

    Driver Version:  4.2.12337 Compatibility Profile Context 13.101
    Desktop Color Depth: 24 bits per pixel
    Monitor Refresh Rate: 60 Hz
    VendorID:  0x1002
    DeviceID:  0x6758
    Number of Monitors:  2
    Number of Logical Video Cards:  1
    Primary Display Resolution:  1920 x 1080
    Desktop Resolution: 3840 x 1080
    Primary Display Size: 20,08" x 11,42"  (23,07" diag)
                                            51,0cm x 29,0cm  (58,6cm diag)
    Primary VRAM Not Detected
Sound card:
    Audio device: Realtek ALC887-VD
    RAM:  3936 Mb
    UI Language:  English
    LANG:  de_DE.UTF-8
    Microphone:  Not set
    Total Hard Disk Space Available:  1220478 Mb
    Largest Free Hard Disk Block:  1127232 Mb
Installed software:
Recent Failure Reports: