Application: kwin (4.6.5 (4.6.5))
KDE Platform Version: 4.6.5 (4.6.5)
Qt Version: 4.7.3
Operating System: Linux 3.0.0-1-amd64 x86_64
Distribution: Debian GNU/Linux unstable (sid)

-- Information about the crash:
- What I was doing when the application crashed:

Kwin will crash when enabling compositing from System Settings, or on start up if compositing is enabled.

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  __memmove_ssse3 () at ../sysdeps/x86_64/multiarch/memcpy-ssse3.S:119
#7  0x00007f986c67cd4b in ?? () from /usr/lib/x86_64-linux-gnu/libGL.so.1
#8  0x00007f9854f6ca8f in KWin::ARBBlurShader::init (this=0x2139300) at ../../../kwin/effects/blur/blurshader.cpp:473
#9  0x00007f9854f69dfb in KWin::BlurEffect::reconfigure (this=0x2138370, flags=<optimized out>) at ../../../kwin/effects/blur/blur.cpp:76
#10 0x00007f9854f69f87 in KWin::BlurEffect::BlurEffect (this=0x2138370) at ../../../kwin/effects/blur/blur.cpp:48
#11 0x00007f9854f6a036 in KWin::effect_create_kwin4_effect_blur () at ../../../kwin/effects/blur/blur.cpp:29
#12 0x00007f986f1875c1 in KWin::EffectsHandlerImpl::loadEffect (this=0x2001ca0, name=...) at ../../kwin/effects.cpp:1128
#13 0x00007f986f188689 in KWin::EffectsHandlerImpl::reconfigure (this=0x2001ca0) at ../../kwin/effects.cpp:143
#14 0x00007f986f16222a in KWin::Workspace::setupCompositing (this=0x7f985004b990) at ../../kwin/composite.cpp:216
#15 0x00007f986f0e66d3 in KWin::Workspace::Workspace (this=0x7f985004b990, restore=false) at ../../kwin/workspace.cpp:222
#16 0x00007f986f0fd76a in KWin::Application::Application (this=<optimized out>) at ../../kwin/main.cpp:331
#17 0x00007f986f0ff47b in kdemain (argc=<optimized out>, argv=<optimized out>) at ../../kwin/main.cpp:506
#18 0x00007f986ed3dead in __libc_start_main (main=<optimized out>, argc=<optimized out>, ubp_av=<optimized out>, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffffa8e27b8) at libc-start.c:228
#19 0x00000000004006a1 in _start ()

Reported using DrKonqi