Comment 3 for bug 338205

OK, got a backtrace:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb4c79710 (LWP 14855)]
0xb663ceba in QTimer::stop () from /usr/lib/libQtCore.so.4
(gdb) bt
#0 0xb663ceba in QTimer::stop () from /usr/lib/libQtCore.so.4
#1 0xb7f9f880 in PanelView::updatePanelGeometry (this=0x989f510)
    at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/panelview.cpp:543
#2 0xb7fa44ab in PanelView::qt_metacall (this=0x989f510, _c=QMetaObject::InvokeMetaMethod, _id=16, _a=0xbfa109d8)
    at /build/buildd/kdebase-workspace-4.2.1a/obj-i486-linux-gnu/plasma/shells/desktop/panelview.moc:112
#3 0xb6637cb8 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#4 0xb6638942 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#5 0xb7e9b547 in Plasma::View::sceneRectAboutToChange () from /usr/lib/libplasma.so.3
#6 0xb7e9c7af in ?? () from /usr/lib/libplasma.so.3
#7 0xb7e9bcab in Plasma::View::qt_metacall () from /usr/lib/libplasma.so.3
#8 0xb7fa446a in PanelView::qt_metacall (this=0x989f510, _c=QMetaObject::InvokeMetaMethod, _id=43, _a=0xbfa10c18)
    at /build/buildd/kdebase-workspace-4.2.1a/obj-i486-linux-gnu/plasma/shells/desktop/panelview.moc:91
#9 0xb6637cb8 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#10 0xb6638942 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#11 0xb7e1c127 in Plasma::Applet::geometryChanged () from /usr/lib/libplasma.so.3
#12 0xb7e22930 in Plasma::Applet::itemChange () from /usr/lib/libplasma.so.3
#13 0xb7e3a2bf in Plasma::Containment::itemChange () from /usr/lib/libplasma.so.3
#14 0xb6f07e27 in ?? () from /usr/lib/libQtGui.so.4
#15 0xb6f08053 in QGraphicsItem::setPos () from /usr/lib/libQtGui.so.4
#16 0xb7e38cca in ?? () from /usr/lib/libplasma.so.3
#17 0xb7e3a3c8 in Plasma::Containment::resizeEvent () from /usr/lib/libplasma.so.3
#18 0xb6f520ba in QGraphicsWidget::event () from /usr/lib/libQtGui.so.4
#19 0xb68cef5c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#20 0xb68d723e in QApplication::notify () from /usr/lib/libQtGui.so.4
#21 0xb772471d in KApplication::notify () from /usr/lib/libkdeui.so.5
#22 0xb6621a4b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#23 0xb68da0de in QCoreApplication::sendEvent () from /usr/lib/libQtGui.so.4
#24 0xb6f53185 in QGraphicsWidget::setGeometry () from /usr/lib/libQtGui.so.4
#25 0xb6f50771 in QGraphicsWidget::resize () from /usr/lib/libQtGui.so.4
#26 0xb7fa1103 in PanelView::pinchContainment (this=0x989f510, screenGeom=@0xbfa11a00)
    at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/panelview.cpp:618
#27 0xb7fa2658 in PanelView (this=0x989f510, panel=0x95b5b78, id=1, parent=0x0)
    at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/panelview.cpp:243
#28 0xb7fac246 in PlasmaApp::createView (this=0x949a998, containment=0x95b5b78)
    at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/plasmaapp.cpp:619
#29 0xb7fac966 in PlasmaApp::containmentAdded (this=0x949a998, containment=0x95b5b78)
    at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/plasmaapp.cpp:663
#30 0xb7facbdc in PlasmaApp::qt_metacall (this=0x949a998, _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0xbfa11d0c)
    at /build/buildd/kdebase-workspace-4.2.1a/obj-i486-linux-gnu/plasma/shells/desktop/plasmaapp.moc:97
#31 0xb6637cb8 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#32 0xb6638942 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#33 0xb7e3e2d3 in Plasma::Corona::containmentAdded () from /usr/lib/libplasma.so.3
#34 0xb7e3f8d8 in Plasma::Corona::loadLayout () from /usr/lib/libplasma.so.3
#35 0xb7e40ff1 in Plasma::Corona::initializeLayout () from /usr/lib/libplasma.so.3
#36 0xb7fa958d in PlasmaApp::corona (this=0x949a998) at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/plasmaapp.cpp:517
#37 0xb7fa9ba5 in PlasmaApp::setupDesktop (this=0x949a998) at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/plasmaapp.cpp:255
#38 0xb7facc0b in PlasmaApp::qt_metacall (this=0x949a998, _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfa12008)
    at /build/buildd/kdebase-workspace-4.2.1a/obj-i486-linux-gnu/plasma/shells/desktop/plasmaapp.moc:95
#39 0xb6637cb8 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#40 0xb6638942 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
---Type <return> to continue, or q <return> to quit---
#41 0xb663d0b7 in ?? () from /usr/lib/libQtCore.so.4
#42 0xb663d1dc in ?? () from /usr/lib/libQtCore.so.4
#43 0xb663216f in QObject::event () from /usr/lib/libQtCore.so.4
#44 0xb68cef5c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#45 0xb68d723e in QApplication::notify () from /usr/lib/libQtGui.so.4
#46 0xb772471d in KApplication::notify () from /usr/lib/libkdeui.so.5
#47 0xb6621a4b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#48 0xb6650d81 in ?? () from /usr/lib/libQtCore.so.4
#49 0xb664d4f0 in ?? () from /usr/lib/libQtCore.so.4
#50 0xb4f84af8 in IA__g_main_context_dispatch (context=0x94bd490) at /build/buildd/glib2.0-2.19.10/glib/gmain.c:1814
#51 0xb4f8805b in g_main_context_iterate (context=0x94bd490, block=1, dispatch=1, self=0x94bae30)
    at /build/buildd/glib2.0-2.19.10/glib/gmain.c:2448
#52 0xb4f881d8 in IA__g_main_context_iteration (context=0x94bd490, may_block=1) at /build/buildd/glib2.0-2.19.10/glib/gmain.c:2511
#53 0xb664d448 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#54 0xb6970405 in ?? () from /usr/lib/libQtGui.so.4
#55 0xb662007a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#56 0xb66204ba in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#57 0xb6622969 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#58 0xb68cedd7 in QApplication::exec () from /usr/lib/libQtGui.so.4
#59 0xb7f95826 in kdemain (argc=1, argv=0xbfa12864) at /build/buildd/kdebase-workspace-4.2.1a/plasma/shells/desktop/main.cpp:54
#60 0x08048712 in main (argc=Cannot access memory at address 0x21
) at /build/buildd/kdebase-workspace-4.2.1a/obj-i486-linux-gnu/plasma/shells/desktop/plasma_qgv_dummy.cpp:3

Disassembly, ending at the faulting instruction:
(gdb) disassemble
Dump of assembler code for function _ZN6QTimer4stopEv:
0xb663cea0 <_ZN6QTimer4stopEv+0>: push %ebp
0xb663cea1 <_ZN6QTimer4stopEv+1>: mov %esp,%ebp
0xb663cea3 <_ZN6QTimer4stopEv+3>: sub $0x18,%esp
0xb663cea6 <_ZN6QTimer4stopEv+6>: mov %esi,-0x4(%ebp)
0xb663cea9 <_ZN6QTimer4stopEv+9>: mov 0x8(%ebp),%esi
0xb663ceac <_ZN6QTimer4stopEv+12>: mov %ebx,-0x8(%ebp)
0xb663ceaf <_ZN6QTimer4stopEv+15>: call 0xb651b207 <_ZNK11QTextStream13flagsInternalEv@plt+199>
0xb663ceb4 <_ZN6QTimer4stopEv+20>: add $0xd8140,%ebx
0xb663ceba <_ZN6QTimer4stopEv+26>: mov 0x8(%esi),%eax

Looks like esi is a null pointer here, hence the invalid reference to address 0x8:

(gdb) info registers
eax 0x0 0
ecx 0x21 33
edx 0x989f920 160037152
ebx 0xb6714ff4 -1234087948
esp 0xbfa10780 0xbfa10780
ebp 0xbfa10798 0xbfa10798
esi 0x0 0
edi 0x98a76f8 160069368
eip 0xb663ceba 0xb663ceba <QTimer::stop()+26>
eflags 0x210282 [ SF IF RF ID ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51