I have this strange graphics artifacts only on MVM

This is with motion blur enabled - picture is too bright and blurred

This is without motion blur. In game it looks like new frames are added to old ones

My system info:

Processor Information:
Vendor: AuthenticAMD
Speed: 2800 Mhz
2 logical processors
2 physical processors
HyperThreading: Unsupported
FCMOV: Supported
SSE2: Supported
SSE3: Supported
SSSE3: Unsupported
SSE4a: Supported
SSE41: Unsupported
SSE42: Unsupported

Network Information:
Network Speed:

Operating System Version:
Ubuntu 13.04 (64 bit)
Kernel Name: Linux
Kernel Version: 3.9.0-030900-generic
X Server Vendor: The X.Org Foundation
X Server Release: 11303000
X Window Manager: Metacity
Steam Runtime Version: steam-runtime-release-i386_2013-04-16

Video Card:
Driver: ATI Technologies Inc. AMD Radeon HD 6900 Series

Driver Version:  4.2.12217 Compatibility Profile Context 12.104
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 59 Hz
VendorID:  0x1002
DeviceID:  0x671f
Number of Monitors:  1
Number of Logical Video Cards:  1
Primary Display Resolution:  2560 x 1440
Desktop Resolution: 2560 x 1440
Primary Display Size: 23,50" x 13,23"  (26,97" diag)
                                        59,7cm x 33,6cm  (68,5cm diag)
Primary VRAM Not Detected

Sound card:
Audio device: Realtek ALC887-VD

Memory:
RAM: 7982 Mb

Miscellaneous:
UI Language: English
LANG: en_US.UTF-8
Microphone: Not set
Total Hard Disk Space Available: 323930 Mb
Largest Free Hard Disk Block: 206470 Mb

Installed software:

Recent Failure Reports: