Version:            (using KDE 4.1.2)
Installed from:    Compiled From Sources

Version: Krita 2 Beta 2 from svn
Fedora 9 
KDE4.1.2

How to reproduce:
Select duplicate and try to duplicate some pixels. 

Here is crash log

Application: Krita (krita), signal SIGABRT
[Thread debugging using libthread_db enabled]
[New Thread 0xb7f75790 (LWP 3526)]
[New Thread 0xb42feb90 (LWP 3539)]
[KCrash handler]
#6  0x00110416 in __kernel_vsyscall ()
#7  0x08527660 in raise () from /lib/libc.so.6
#8  0x08529028 in abort () from /lib/libc.so.6
#9  0x00111f1a in qtMessageHandler (type=QtFatalMsg, 
    msg=0xb42fbf0c "ASSERT: \"d\" in file /home/lukas/src/koffice/krita/image/kis_shared_ptr.h, line 180") at /home/lukas/src/koffice/krita/main.cc:36
#10 0x00e68295 in qt_message_output () from /usr/lib/libQtCore.so.4
#11 0x00e683d2 in qFatal () from /usr/lib/libQtCore.so.4
#12 0x00e68475 in qt_assert () from /usr/lib/libQtCore.so.4
#13 0x0162393d in KisSharedPtr<KisBrush>::operator-> (this=0x9d60848)
    at /home/lukas/src/koffice/krita/image/kis_shared_ptr.h:180
#14 0x01623633 in KisBrushBasedPaintOp::spacing (this=0x9d60838, 
    xSpacing=@0xb42fe0b8, ySpacing=@0xb42fe0b0, pressure1=0.5, pressure2=0.5)
    at /home/lukas/src/koffice/krita/plugins/paintops/libpaintop/kis_brush_based_paintop.cpp:33
#15 0x00439162 in KisPaintOp::paintLine (this=0x9d60838, pi1=@0x9dcd78c, 
    pi2=@0x9dcd790, savedDist=0)
    at /home/lukas/src/koffice/krita/image/kis_paintop.cc:157
#16 0x00420e8b in KisPainter::paintLine (this=0x9df02b0, pi1=@0x9dcd78c, 
    pi2=@0x9dcd790, savedDist=0)
    at /home/lukas/src/koffice/krita/image/kis_painter.cc:501
#17 0x002adb77 in FreehandPaintLineJob::run (this=0x9dcd778)
    at /home/lukas/src/koffice/krita/ui/tool/kis_tool_freehand_p.cpp:84
#18 0x002acde5 in FreehandPaintJobExecutor::run (this=0x900bcb0)
    at /home/lukas/src/koffice/krita/ui/tool/kis_tool_freehand_p.h:153
#19 0x00e70232 in ?? () from /usr/lib/libQtCore.so.4
#20 0x0091d32f in start_thread () from /lib/libpthread.so.0
#21 0x085db20e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb7f75790 (LWP 3526)):
#0  0x00110416 in __kernel_vsyscall ()
#1  0x085d3671 in select () from /lib/libc.so.6
#2  0x011eb295 in ?? () from /usr/lib/libxcb.so.1
#3  0x011ecc82 in xcb_wait_for_reply () from /usr/lib/libxcb.so.1
#4  0x06247e41 in _XReply () from /usr/lib/libX11.so.6
#5  0x06224089 in XGetImage () from /usr/lib/libX11.so.6
#6  0x04bebaff in ?? () from /usr/lib/libQtGui.so.4
#7  0x04bddf6b in QPixmap::toImage () from /usr/lib/libQtGui.so.4
#8  0x04c08316 in QBrush::textureImage () from /usr/lib/libQtGui.so.4
#9  0x04c9e5c1 in ?? () from /usr/lib/libQtGui.so.4
#10 0x04c9ff0c in ?? () from /usr/lib/libQtGui.so.4
#11 0x04c1fddb in ?? () from /usr/lib/libQtGui.so.4
#12 0x04c1feab in ?? () from /usr/lib/libQtGui.so.4
#13 0x04c2a2a1 in QPainter::drawPath () from /usr/lib/libQtGui.so.4
#14 0x04c25093 in ?? () from /usr/lib/libQtGui.so.4
#15 0x04c278b2 in QPainter::drawRects () from /usr/lib/libQtGui.so.4
#16 0x04c2980b in QPainter::drawPixmap () from /usr/lib/libQtGui.so.4
#17 0x0120b40f in QPainter::drawRoundRect ()
   from /usr/lib/kde4/plugins/styles/oxygen.so
#18 0x0121bb50 in ?? () from /usr/lib/kde4/plugins/styles/oxygen.so
#19 0x00f5f91a in QCoreApplicationPrivate::sendThroughObjectEventFilters ()
   from /usr/lib/libQtCore.so.4
#20 0x04b182ea in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#21 0x04b2023a in QApplication::notify () from /usr/lib/libQtGui.so.4
#22 0x05d6847d in KApplication::notify () from /usr/lib/libkdeui.so.5
#23 0x00f60731 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#24 0x04b78b8e in ?? () from /usr/lib/libQtGui.so.4
#25 0x04b6e8d0 in QWidgetPrivate::drawWidget () from /usr/lib/libQtGui.so.4
#26 0x04cdb287 in ?? () from /usr/lib/libQtGui.so.4
#27 0x04cdc097 in ?? () from /usr/lib/libQtGui.so.4
#28 0x04b6fcd6 in QWidget::event () from /usr/lib/libQtGui.so.4
#29 0x04ec25c7 in QMainWindow::event () from /usr/lib/libQtGui.so.4
#30 0x05e2d118 in KMainWindow::event () from /usr/lib/libkdeui.so.5
#31 0x05e6e9fc in KXmlGuiWindow::event () from /usr/lib/libkdeui.so.5
#32 0x04b1830c in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#33 0x04b2023a in QApplication::notify () from /usr/lib/libQtGui.so.4
#34 0x05d6847d in KApplication::notify () from /usr/lib/libkdeui.so.5
#35 0x00f60731 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#36 0x00f613a5 in QCoreApplicationPrivate::sendPostedEvents ()
   from /usr/lib/libQtCore.so.4
#37 0x00f615bd in QCoreApplication::sendPostedEvents ()
   from /usr/lib/libQtCore.so.4
#38 0x00f8b25f in ?? () from /usr/lib/libQtCore.so.4
#39 0x06158008 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#40 0x0615b6b3 in ?? () from /lib/libglib-2.0.so.0
#41 0x0615b871 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#42 0x00f8aea8 in QEventDispatcherGlib::processEvents ()
   from /usr/lib/libQtCore.so.4
#43 0x04bb0d95 in ?? () from /usr/lib/libQtGui.so.4
#44 0x00f5ee1a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#45 0x00f5efda in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#46 0x00f61685 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#47 0x04b18187 in QApplication::exec () from /usr/lib/libQtGui.so.4
#48 0x001134e6 in kdemain (argc=1, argv=0xbf8ad974)
    at /home/lukas/src/koffice/krita/main.cc:56
#49 0x080489c6 in main (argc=256, argv=0x0)
    at /home/lukas/src/build/koffice/krita/krita_dummy.cpp:3