I just updated Krita (and the rest of the Calligra suite) to version 2.5.3-0ubuntu2 from the Quantal repositories. The crash is still all the same there. I'm using the latest free Radeon driver here.
Looking at the Backtrace below, I can see that it refers to two different versions of libllvm: 3.0 in #8 and 3.1 in #9. I'm no programmer, but that doesn't look right to me.

Backtrace:

Thread 1 (Thread 0x7f1d833e6780 (LWP 5800)):
[KCrash Handler]
#6  0x00007f1d631d508e in llvm::cl::parser<llvm::FunctionPass* (*)()>::getOption(unsigned int) const () from /usr/lib/x86_64-linux-gnu/libLLVM-3.0.so.1
#7  0x00007f1d637947a8 in llvm::cl::generic_parser_base::findOption(char const*) () from /usr/lib/x86_64-linux-gnu/libLLVM-3.0.so.1
#8  0x00007f1d631d511d in llvm::RegisterPassParser<llvm::RegisterRegAlloc>::NotifyRemove(char const*) () from /usr/lib/x86_64-linux-gnu/libLLVM-3.0.so.1
#9  0x00007f1d28978a1c in ?? () from /usr/lib/x86_64-linux-gnu/libLLVM-3.1.so.1
#10 0x00007f1d83216316 in call_init (l=<optimized out>, argc=1, argv=0x7fff6689bb68, env=0x90ed90) at dl-init.c:85
#11 0x00007f1d832163ef in call_init (env=<optimized out>, argv=<optimized out>, argc=<optimized out>, l=<optimized out>) at dl-init.c:52
#12 _dl_init (main_map=0x336caa0, argc=1, argv=0x7fff6689bb68, env=0x90ed90) at dl-init.c:134
#13 0x00007f1d8321aaea in dl_open_worker (a=0x7fff66898e50) at dl-open.c:549
#14 0x00007f1d83216186 in _dl_catch_error (objname=0x7fff66898e98, errstring=0x7fff66898ea0, mallocedp=0x7fff66898eaf, operate=0x7f1d8321a710 <dl_open_worker>, args=0x7fff66898e50) at dl-error.c:178
#15 0x00007f1d8321a32a in _dl_open (file=0x7fff668990b0 "/usr/lib/x86_64-linux-gnu/dri/r600_dri.so", mode=-2147483390, caller_dlopen=0x7f1d75f7a808 <driOpenDriver+376>, nsid=-2, argc=1, argv=<optimized out>, env=0x90ed90) at dl-open.c:639
#16 0x00007f1d7a518f26 in dlopen_doit (a=0x7fff66899070) at dlopen.c:67
#17 0x00007f1d83216186 in _dl_catch_error (objname=0x92dd40, errstring=0x92dd48, mallocedp=0x92dd38, operate=0x7f1d7a518ec0 <dlopen_doit>, args=0x7fff66899070) at dl-error.c:178
#18 0x00007f1d7a51952f in _dlerror_run (operate=0x7f1d7a518ec0 <dlopen_doit>, args=0x7fff66899070) at dlerror.c:164
#19 0x00007f1d7a518fc1 in __dlopen (file=<optimized out>, file@entry=0x7fff668990b0 "/usr/lib/x86_64-linux-gnu/dri/r600_dri.so", mode=<optimized out>, mode@entry=258) at dlopen.c:88
#20 0x00007f1d75f7a808 in driOpenDriver (driverName=0x3e23370 "r600") at dri_common.c:172
#21 0x00007f1d75f7e003 in dri2CreateScreen (screen=0, priv=0x346ce70) at dri2_glx.c:1037
#22 0x00007f1d75f58399 in AllocAndFetchScreenConfigs (priv=0x346ce70, dpy=0x96c7c0) at glxext.c:780
#23 __glXInitialize (dpy=0x96c7c0) at glxext.c:885
#24 __glXInitialize (dpy=dpy@entry=0x96c7c0) at glxext.c:803
#25 0x00007f1d75f54ab9 in GetGLXPrivScreenConfig (dpy=dpy@entry=0x96c7c0, scrn=scrn@entry=0, ppriv=ppriv@entry=0x7fff668992b0, ppsc=ppsc@entry=0x7fff668992b8) at glxcmds.c:176
#26 0x00007f1d75f5525b in GetGLXPrivScreenConfig (ppsc=0x7fff668992b8, ppriv=0x7fff668992b0, scrn=<optimized out>, dpy=0x96c7c0) at glxcmds.c:172
#27 glXChooseVisual (dpy=0x96c7c0, screen=0, attribList=0x7fff66899460) at glxcmds.c:1234
#28 0x00007f1d78a73a42 in QGLContext::tryVisual (this=<optimized out>, f=..., bufDepth=<optimized out>) at qgl_x11.cpp:889
#29 0x00007f1d78a73733 in QGLContext::chooseVisual (this=0x3e45c80) at qgl_x11.cpp:776
#30 0x00007f1d78a765da in QGLContext::chooseContext (this=0x3e45c80, shareContext=0x0) at qgl_x11.cpp:573
#31 0x00007f1d789fd72d in QGLContext::create (this=0x3e45c80, shareContext=0x0) at qgl.cpp:3348
#32 0x00007f1d78a75f47 in QGLWidget::setContext (this=0x4dfb0f0, context=<optimized out>, shareContext=<optimized out>, deleteOldContext=<optimized out>) at qgl_x11.cpp:1512
#33 0x00007f1d789fc79a in QGLWidgetPrivate::initContext (this=0x429f890, context=0x3e45c80, shareWidget=0x0) at qgl.cpp:5603
#34 0x00007f1d78a749da in QGLWidgetPrivate::init (this=0x429f890, context=0x3e45c80, shareWidget=0x0) at qgl_x11.cpp:1357
#35 0x00007f1d789fd5c5 in QGLWidget::QGLWidget (this=0x4dfb0f0, parent=<optimized out>, shareWidget=0x0, f=...) at qgl.cpp:3834
#36 0x00007f1d6c82a754 in KisOpenGL::createContext () at /build/buildd/calligra-2.5.3/krita/ui/opengl/kis_opengl.cpp:39
#37 0x00007f1d6c82a991 in KisOpenGL::hasShadingLanguage () at /build/buildd/calligra-2.5.3/krita/ui/opengl/kis_opengl.cpp:82
#38 0x00007f1d6c715742 in DisplaySettingsTab::DisplaySettingsTab (this=0xb6e1c0, parent=<optimized out>, name=0x0) at /build/buildd/calligra-2.5.3/krita/ui/dialogs/kis_dlg_preferences.cc:374
#39 0x00007f1d6c717a62 in KisDlgPreferences::KisDlgPreferences (this=0x4dee630, parent=<optimized out>, name=<optimized out>) at /build/buildd/calligra-2.5.3/krita/ui/dialogs/kis_dlg_preferences.cc:585
#40 0x00007f1d6c718b76 in KisDlgPreferences::editPreferences () at /build/buildd/calligra-2.5.3/krita/ui/dialogs/kis_dlg_preferences.cc:681
#41 0x00007f1d6c7e1c5e in KisView2::slotPreferences (this=0x98bfd0) at /build/buildd/calligra-2.5.3/krita/ui/kis_view2.cpp:875
#42 0x00007f1d80d61f5f in QMetaObject::activate (sender=0x4269b20, m=<optimized out>, local_signal_index=<optimized out>, argv=0x7fff6689a3e0) at kernel/qobject.cpp:3547
#43 0x00007f1d81727a32 in QAction::triggered (this=this@entry=0x4269b20, _t1=false) at .moc/release-shared/moc_qaction.cpp:277
#44 0x00007f1d81727c20 in QAction::activate (this=0x4269b20, event=<optimized out>) at kernel/qaction.cpp:1257
#45 0x00007f1d81b663d3 in QMenuPrivate::activateCausedStack (this=this@entry=0x3336570, causedStack=..., action=action@entry=0x4269b20, action_e=action_e@entry=QAction::Trigger, self=self@entry=true) at widgets/qmenu.cpp:1028
#46 0x00007f1d81b6c6b9 in QMenuPrivate::activateAction (this=0x3336570, action=0x4269b20, action_e=QAction::Trigger, self=<optimized out>) at widgets/qmenu.cpp:1120
#47 0x00007f1d824ef090 in KMenu::mouseReleaseEvent (this=0x3315350, e=0x7fff6689af80) at ../../kdeui/widgets/kmenu.cpp:464
#48 0x00007f1d8177d850 in QWidget::event (this=0x3315350, event=0x7fff6689af80) at kernel/qwidget.cpp:8371
#49 0x00007f1d81b6d96b in QMenu::event (this=0x3315350, e=0x7fff6689af80) at widgets/qmenu.cpp:2469
#50 0x00007f1d8172de9c in QApplicationPrivate::notify_helper (this=this@entry=0x945710, receiver=receiver@entry=0x3315350, e=e@entry=0x7fff6689af80) at kernel/qapplication.cpp:4562
#51 0x00007f1d81732b6b in QApplication::notify (this=<optimized out>, receiver=0x3315350, e=0x7fff6689af80) at kernel/qapplication.cpp:4105
#52 0x00007f1d824361d6 in KApplication::notify (this=0x7fff6689ba50, receiver=0x3315350, event=0x7fff6689af80) at ../../kdeui/kernel/kapplication.cpp:311
#53 0x00007f1d80d4c56e in QCoreApplication::notifyInternal (this=0x7fff6689ba50, receiver=0x3315350, event=0x7fff6689af80) at kernel/qcoreapplication.cpp:915
#54 0x00007f1d8172ecd3 in sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#55 QApplicationPrivate::sendMouseEvent (receiver=0x3315350, event=0x7fff6689af80, alienWidget=0x0, nativeWidget=0x3315350, buttonDown=0x7f1d8220a308 <qt_button_down>, lastMouseReceiver=..., spontaneous=true) at kernel/qapplication.cpp:3173
#56 0x00007f1d817ac41c in QETWidget::translateMouseEvent (this=this@entry=0x3315350, event=event@entry=0x7fff6689b710) at kernel/qapplication_x11.cpp:4556
#57 0x00007f1d817ab44f in QApplication::x11ProcessEvent (this=0x7fff6689ba50, event=0x7fff6689b710) at kernel/qapplication_x11.cpp:3737
#58 0x00007f1d817d39d9 in QEventDispatcherX11::processEvents (this=0x8b7b30, flags=...) at kernel/qeventdispatcher_x11.cpp:132
#59 0x00007f1d80d4b2bf in QEventLoop::processEvents (this=this@entry=0x7fff6689b980, flags=...) at kernel/qeventloop.cpp:149
#60 0x00007f1d80d4b548 in QEventLoop::exec (this=0x7fff6689b980, flags=...) at kernel/qeventloop.cpp:204
#61 0x00007f1d80d50708 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1187
#62 0x00007f1d82f85712 in kdemain (argc=<optimized out>, argv=<optimized out>) at /build/buildd/calligra-2.5.3/krita/main.cc:79
#63 0x00007f1d82bde76d in __libc_start_main (main=0x400690 <main(int, char**)>, argc=1, ubp_av=0x7fff6689bb68, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff6689bb58) at libc-start.c:226
#64 0x00000000004006c1 in _start ()