Application that crashed: konqueror
Version of the application: 4.2.95 (KDE 4.2.95 (KDE 4.3 RC1))
KDE Version: 4.2.95 (KDE 4.2.95 (KDE 4.3 RC1))
Qt Version: 4.5.1
Operating System: Linux 2.6.28-11-generic i686
Distribution: Ubuntu 9.04

What I was doing when the application crashed:
Application: Konqueror 4.3 RC1

Open Konqueror with the default start page.
From the extra toolbar, used Split View Top/Bottom twice and then keep clicking "Close Active View" to see the crash.

 -- Backtrace:
Application: Konqueror (kdeinit4), signal: Segmentation fault
[KCrash Handler]
#6  0xb767c780 in KTabWidget::tabBarWidthForMaxChars () from /usr/lib/libkdeui.so.5
#7  0xb767cdb6 in KTabWidget::Private::resizeTabs () from /usr/lib/libkdeui.so.5
#8  0xb767ce7c in KTabWidget::resizeEvent () from /usr/lib/libkdeui.so.5
#9  0xb6a8d6d6 in QWidget::event () from /usr/lib/libQtGui.so.4
#10 0xb6eebf23 in QTabWidget::event () from /usr/lib/libQtGui.so.4
#11 0xb6a36bcc in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#12 0xb6a3efc2 in QApplication::notify () from /usr/lib/libQtGui.so.4
#13 0xb75703dd in KApplication::notify () from /usr/lib/libkdeui.so.5
#14 0xb7f9c49b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#15 0xb6acf2b6 in QWidgetPrivate::setGeometry_sys () from /usr/lib/libQtGui.so.4
#16 0xb6a8c508 in QWidget::setGeometry () from /usr/lib/libQtGui.so.4
#17 0xb6f225e0 in ?? () from /usr/lib/libQtGui.so.4
#18 0xb6e60155 in ?? () from /usr/lib/libQtGui.so.4
#19 0xb6e8b202 in ?? () from /usr/lib/libQtGui.so.4
#20 0xb6e8c87a in ?? () from /usr/lib/libQtGui.so.4
#21 0xb6e8cfb8 in ?? () from /usr/lib/libQtGui.so.4
#22 0xb6a648cc in QLayoutPrivate::doResize () from /usr/lib/libQtGui.so.4
#23 0xb6a64a05 in QLayout::activate () from /usr/lib/libQtGui.so.4
#24 0xb6a9366b in QWidget::setVisible () from /usr/lib/libQtGui.so.4
#25 0xb768c989 in KToolBar::applySettings () from /usr/lib/libkdeui.so.5
#26 0xb76579d3 in KMainWindow::applyMainWindowSettings () from /usr/lib/libkdeui.so.5
#27 0xb769a8a7 in KXmlGuiWindow::applyMainWindowSettings () from /usr/lib/libkdeui.so.5
#28 0xb7699ec6 in KXmlGuiWindow::finalizeGUI () from /usr/lib/libkdeui.so.5
#29 0xb7697650 in KXMLGUIBuilder::finalizeGUI () from /usr/lib/libkdeui.so.5
#30 0xb7699e27 in KXmlGuiWindow::finalizeGUI () from /usr/lib/libkdeui.so.5
#31 0xb76a88be in KXMLGUIFactory::addClient () from /usr/lib/libkdeui.so.5
#32 0xb7c0bb37 in KParts::MainWindow::createGUI () from /usr/lib/libkparts.so.4
#33 0xb3bb7813 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#34 0xb3b6c3e1 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#35 0xb3b6c51b in ?? () from /usr/lib/libkdeinit4_konqueror.so
#36 0xb3b79e10 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#37 0xb3b7fa33 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#38 0xb3b85bcc in ?? () from /usr/lib/libkdeinit4_konqueror.so
#39 0xb7fb2748 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#40 0xb7fb33d2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#41 0xb6eeadf3 in QTabWidget::currentChanged () from /usr/lib/libQtGui.so.4
#42 0xb6eecf44 in ?? () from /usr/lib/libQtGui.so.4
#43 0xb6eed0f7 in QTabWidget::qt_metacall () from /usr/lib/libQtGui.so.4
#44 0xb767d5ba in KTabWidget::qt_metacall () from /usr/lib/libkdeui.so.5
#45 0xb3b85a1a in ?? () from /usr/lib/libkdeinit4_konqueror.so
#46 0xb7fb2748 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#47 0xb7fb33d2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#48 0xb6ede643 in QTabBar::currentChanged () from /usr/lib/libQtGui.so.4
#49 0xb6ee5815 in QTabBar::setCurrentIndex () from /usr/lib/libQtGui.so.4
#50 0xb6ee85f2 in QTabBar::insertTab () from /usr/lib/libQtGui.so.4
#51 0xb6eecba7 in QTabWidget::insertTab () from /usr/lib/libQtGui.so.4
#52 0xb6eecc29 in QTabWidget::insertTab () from /usr/lib/libQtGui.so.4
#53 0xb3b82178 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#54 0xb3b7f72f in ?? () from /usr/lib/libkdeinit4_konqueror.so
#55 0xb3b75244 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#56 0xb3bb4637 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#57 0xb3bc7630 in ?? () from /usr/lib/libkdeinit4_konqueror.so
#58 0xb7fb2748 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#59 0xb7fb2b80 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#60 0xb6a30551 in QAction::triggered () from /usr/lib/libQtGui.so.4
#61 0xb6a31acf in QAction::activate () from /usr/lib/libQtGui.so.4
#62 0xb6f04d12 in QToolButton::nextCheckState () from /usr/lib/libQtGui.so.4
#63 0xb6e1d573 in ?? () from /usr/lib/libQtGui.so.4
#64 0xb6e1d846 in QAbstractButton::mouseReleaseEvent () from /usr/lib/libQtGui.so.4
#65 0xb6f0520c in QToolButton::mouseReleaseEvent () from /usr/lib/libQtGui.so.4
#66 0xb6a8d8c3 in QWidget::event () from /usr/lib/libQtGui.so.4
#67 0xb6e1b81e in QAbstractButton::event () from /usr/lib/libQtGui.so.4
#68 0xb6f07c3a in QToolButton::event () from /usr/lib/libQtGui.so.4
#69 0xb6a36bcc in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#70 0xb6a3f851 in QApplication::notify () from /usr/lib/libQtGui.so.4
#71 0xb75703dd in KApplication::notify () from /usr/lib/libkdeui.so.5
#72 0xb7f9c49b in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#73 0xb6a3e8be in QApplicationPrivate::sendMouseEvent () from /usr/lib/libQtGui.so.4
#74 0xb6aaeaee in ?? () from /usr/lib/libQtGui.so.4
#75 0xb6aadead in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#76 0xb6ad906a in ?? () from /usr/lib/libQtGui.so.4
#77 0xb65e9b88 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#78 0xb65ed0eb in ?? () from /usr/lib/libglib-2.0.so.0
#79 0xb65ed268 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#80 0xb7fc7ec8 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#81 0xb6ad8765 in ?? () from /usr/lib/libQtGui.so.4
#82 0xb7f9aaca in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#83 0xb7f9af0a in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#84 0xb7f9d3b9 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#85 0xb6a36a47 in QApplication::exec () from /usr/lib/libQtGui.so.4
#86 0xb3bf80e8 in kdemain () from /usr/lib/libkdeinit4_konqueror.so
#87 0x0804e1c0 in _start ()

Reported using DrKonqi