Version:            (using KDE 4.1.3)
OS:                FreeBSD
Installed from:    FreeBSD Ports

I rebuild the index for a big folder (~30k emails).
While it was working (UI freeze), i clicked another folder.
Finally confirmation message popped up saying that the index had been recreated. Then a crash occurred.

Backtrace:

Application: KMail (kmail), signal SIGSEGV
[New Thread 0x2c001100 (LWP 100086)]
[Switching to Thread 0x2c001100 (LWP 100086)]
[KCrash handler]
#6  0x281ee73c in KMHeaders::writeSortOrder ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#7  0x281fbefe in KMHeaders::setFolder ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#8  0x28436b26 in KMMainWidget::folderSelected ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#9  0x2843b8d4 in KMMainWidget::qt_metacall ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#10 0x2a685fec in QMetaObject::activate ()
   from /usr/local/lib/qt4/libQtCore.so.4
#11 0x2a686422 in QMetaObject::activate ()
   from /usr/local/lib/qt4/libQtCore.so.4
#12 0x281ccf03 in KMFolderTree::folderSelected ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#13 0x281d1f43 in KMFolderTree::doFolderSelected ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#14 0x281d20b4 in KMFolderTree::contentsMouseReleaseEvent ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#15 0x2968dc11 in Q3ScrollView::viewportMouseReleaseEvent ()
   from /usr/local/lib/qt4/libQt3Support.so.4
#16 0x2968f758 in Q3ScrollView::eventFilter ()
   from /usr/local/lib/qt4/libQt3Support.so.4
#17 0x2963d486 in Q3ListView::eventFilter ()
   from /usr/local/lib/qt4/libQt3Support.so.4
#18 0x281cd55a in KMFolderTree::eventFilter ()
   from /usr/local/kde4/lib/libkmailprivate.so.5
#19 0x2a675e81 in QCoreApplicationPrivate::sendThroughObjectEventFilters ()
   from /usr/local/lib/qt4/libQtCore.so.4
#20 0x2ad7e803 in QApplicationPrivate::notify_helper ()
   from /usr/local/lib/qt4/libQtGui.so.4
#21 0x2ad85792 in QApplication::notify ()
   from /usr/local/lib/qt4/libQtGui.so.4
#22 0x29e29813 in KApplication::notify ()
   from /usr/local/kde4/lib/libkdeui.so.7
#23 0x2a675a19 in QCoreApplication::notifyInternal ()
   from /usr/local/lib/qt4/libQtCore.so.4
#24 0x2ad84ea0 in QApplicationPrivate::sendMouseEvent ()
   from /usr/local/lib/qt4/libQtGui.so.4
#25 0x2ade05e0 in QETWidget::translateMouseEvent ()
   from /usr/local/lib/qt4/libQtGui.so.4
#26 0x2addfcaa in QApplication::x11ProcessEvent ()
   from /usr/local/lib/qt4/libQtGui.so.4
#27 0x2ae03cb4 in x11EventSourceDispatch ()
   from /usr/local/lib/qt4/libQtGui.so.4
#28 0x2b9df266 in g_main_context_dispatch ()
   from /usr/local/lib/libglib-2.0.so.0
#29 0x2b9e2602 in g_main_context_check () from /usr/local/lib/libglib-2.0.so.0
#30 0x2b9e2b85 in g_main_context_iteration ()
   from /usr/local/lib/libglib-2.0.so.0
#31 0x2a69ca5e in QEventDispatcherGlib::processEvents ()
   from /usr/local/lib/qt4/libQtCore.so.4
#32 0x2ae03965 in QGuiEventDispatcherGlib::processEvents ()
   from /usr/local/lib/qt4/libQtGui.so.4
#33 0x2a674b93 in QEventLoop::processEvents ()
   from /usr/local/lib/qt4/libQtCore.so.4
#34 0x2a674d21 in QEventLoop::exec () from /usr/local/lib/qt4/libQtCore.so.4
#35 0x2a676f0a in QCoreApplication::exec ()
   from /usr/local/lib/qt4/libQtCore.so.4
#36 0x2ad7ddc7 in QApplication::exec () from /usr/local/lib/qt4/libQtGui.so.4
#37 0x0804a79e in main ()