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 3.0.0-2-amd64 x86_64
Distribution: Debian GNU/Linux unstable (sid)

-- Information about the crash:
Hi,
on trying to activate Compositing in th system settings, Kwin crashed.
Cheers, dietrich

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
[KCrash Handler]
#6  __memcpy_ssse3_back () at ../sysdeps/x86_64/multiarch/memcpy-ssse3-back.S:98
#7  0x00007f5a931cfd4b in __indirect_glProgramParameters4fvNV (target=15399216, index=106336, num=260721920, params=0x19f60) at indirect.c:9317
#8  0x00007f5a7b154aaf in KWin::ARBBlurShader::init (this=0xfd1e00) at ../../../kwin/effects/blur/blurshader.cpp:473
#9  0x00007f5a7b151e1b in KWin::BlurEffect::reconfigure (this=0xfd08c0, flags=<optimized out>) at ../../../kwin/effects/blur/blur.cpp:76
#10 0x00007f5a7b151fa7 in KWin::BlurEffect::BlurEffect (this=0xfd08c0) at ../../../kwin/effects/blur/blur.cpp:48
#11 0x00007f5a7b152056 in KWin::effect_create_kwin4_effect_blur () at ../../../kwin/effects/blur/blur.cpp:29
#12 0x00007f5a95cdb471 in KWin::EffectsHandlerImpl::loadEffect (this=0xeabe80, name=...) at ../../kwin/effects.cpp:1128
#13 0x00007f5a95cdc531 in KWin::EffectsHandlerImpl::reconfigure (this=0xeabe80) at ../../kwin/effects.cpp:143
#14 0x00007f5a95cb631a in KWin::Workspace::setupCompositing (this=0xe472d0) at ../../kwin/composite.cpp:216
#15 0x00007f5a95c3a733 in KWin::Workspace::Workspace (this=0xe472d0, restore=false) at ../../kwin/workspace.cpp:222
#16 0x00007f5a95c517ca in KWin::Application::Application (this=<optimized out>) at ../../kwin/main.cpp:331
#17 0x00007f5a95c534db in kdemain (argc=<optimized out>, argv=<optimized out>) at ../../kwin/main.cpp:506
#18 0x00007f5a95891ead 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=0x7fff3ae7f0f8) at libc-start.c:228
#19 0x00000000004006b1 in _start ()

Reported using DrKonqi