Version:           1.11.0 (using KDE 4.2.0)
OS:                Linux
Installed from:    Gentoo Packages

Occasionally, when switching to a subfolder of inbox, kmail (run within kontact) crashes with the following backtrace:

Application: Kontact (kontact), signal SIGSEGV
0x00007f00099a07e1 in nanosleep () from /lib/libc.so.6
[Current thread is 0 (LWP 32041)]

Thread 2 (Thread 0x42b5a950 (LWP 32056)):
#0  0x00007f00099c80c2 in select () from /lib/libc.so.6
#1  0x00007f000a7151ce in ?? () from /usr/lib64/qt4/libQtCore.so.4
#2  0x00007f000a655142 in ?? () from /usr/lib64/qt4/libQtCore.so.4
#3  0x00007f000a3e5047 in start_thread () from /lib/libpthread.so.0
#4  0x00007f00099ce28d in clone () from /lib/libc.so.6
#5  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f00101aa700 (LWP 32041)):
[KCrash Handler]
#5  0x00007f000b35cb93 in QPainter::worldMatrixEnabled () from /usr/lib64/qt4/libQtGui.so.4
#6  0x00007f000b2c828b in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#7  0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#8  0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#9  0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#10 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#11 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#12 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#13 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#14 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#15 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#16 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#17 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#18 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#19 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#20 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#21 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#22 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#23 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#24 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#25 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#26 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#27 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#28 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#29 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#30 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#31 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#32 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#33 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#34 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#35 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#36 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#37 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#38 0x00007f000b2c8b43 in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#39 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#40 0x00007f000b2c8a7a in QWidgetPrivate::paintSiblingsRecursive () from /usr/lib64/qt4/libQtGui.so.4
#41 0x00007f000b2c80cd in QWidgetPrivate::drawWidget () from /usr/lib64/qt4/libQtGui.so.4
#42 0x00007f000b41579d in ?? () from /usr/lib64/qt4/libQtGui.so.4
#43 0x00007f000b415e42 in ?? () from /usr/lib64/qt4/libQtGui.so.4
#44 0x00007f000b2c93d1 in QWidget::event () from /usr/lib64/qt4/libQtGui.so.4
#45 0x00007f000b5e073b in QMainWindow::event () from /usr/lib64/qt4/libQtGui.so.4
#46 0x00007f000c644cfb in KMainWindow::event () from /usr/lib64/libkdeui.so.5
#47 0x00007f000c67e858 in KXmlGuiWindow::event () from /usr/lib64/libkdeui.so.5
#48 0x00007f000b27d3ae in QApplicationPrivate::notify_helper () from /usr/lib64/qt4/libQtGui.so.4
#49 0x00007f000b281ece in QApplication::notify () from /usr/lib64/qt4/libQtGui.so.4
#50 0x00007f000c57d7cb in KApplication::notify () from /usr/lib64/libkdeui.so.5
#51 0x00007f000a733328 in QCoreApplication::notifyInternal () from /usr/lib64/qt4/libQtCore.so.4
#52 0x00007f000a73418d in QCoreApplicationPrivate::sendPostedEvents () from /usr/lib64/qt4/libQtCore.so.4
#53 0x00007f000a75d603 in QEventDispatcherUNIX::processEvents () from /usr/lib64/qt4/libQtCore.so.4
#54 0x00007f000b302303 in ?? () from /usr/lib64/qt4/libQtGui.so.4
#55 0x00007f000a7326a5 in QEventLoop::processEvents () from /usr/lib64/qt4/libQtCore.so.4
#56 0x00007f000a732808 in QEventLoop::exec () from /usr/lib64/qt4/libQtCore.so.4
#57 0x00007f000a73452e in QCoreApplication::exec () from /usr/lib64/qt4/libQtCore.so.4
#58 0x0000000000404282 in _start ()

I can reproduce this crash then every time I restart kmail. Once I switch to one of the other predefined folders (outbox, sent items etc.) and then to one of the inbox-subfolders, things seem to work.