Version:           4.13 (using KDE 4.1.3)
Compiler:          gcc-4.3.2 
OS:                Linux
Installed from:    Gentoo Packages

Having other problems than this crash, I tried to delete all, i.e. two, existing accounts in quick succession. Result:

Application: KMail (kmail), signal SIGSEGV
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0xb459d6d0 (LWP 8132)]
[KCrash handler]
#6  QString (this=0xbfded4b0, other=@0x630069)
    at /usr/include/qt4/QtCore/qstring.h:676
#7  0xb7a3438c in KCoreConfigSkeleton::currentGroup (this=0x96c4848)
    at /var/tmp/portage/kde-base/kdelibs-4.1.3-r1/work/kdelibs-4.1.3/kdecore/config/kcoreconfigskeleton.cpp:984
#8  0xb6e33c16 in MailTransport::TransportManager::removeTransport (
    this=0x96bc700, id=777010202)
    at /var/tmp/portage/kde-base/kdepimlibs-4.1.3/work/kdepimlibs-4.1.3/mailtransport/transportmanager.cpp:292
#9  0xb6e36093 in MailTransport::TransportManagementWidget::removeClicked (
    this=0x9aaf5b0)
    at /var/tmp/portage/kde-base/kdepimlibs-4.1.3/work/kdepimlibs-4.1.3/mailtransport/transportmanagementwidget.cpp:171
#10 0xb6e36978 in MailTransport::TransportManagementWidget::qt_metacall (
    this=0x9aaf5b0, _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0xbfded62c)
    at /var/tmp/portage/kde-base/kdepimlibs-4.1.3/work/kdepimlibs_build/mailtransport/transportmanagementwidget.moc:78
#11 0xb7efbf39 in QMetaObject::activate (sender=0x9ab2c70, 
    from_signal_index=<value optimized out>, to_signal_index=30, 
    argv=0xbfded62c) at kernel/qobject.cpp:3028
#12 0xb7efc380 in QMetaObject::activate (sender=0x9ab2c70, m=0xb5992364, 
    from_local_signal_index=2, to_local_signal_index=3, argv=0xbfded62c)
    at kernel/qobject.cpp:3118
#13 0xb57bc6c1 in QAbstractButton::clicked (this=0x9ab2c70, _t1=false)
    at .moc/debug-shared/moc_qabstractbutton.cpp:185
#14 0xb54ea5b9 in QAbstractButtonPrivate::emitClicked (this=0x9ab2de0)
    at widgets/qabstractbutton.cpp:544
#15 0xb54ec2c4 in QAbstractButtonPrivate::click (this=0x9ab2de0)
    at widgets/qabstractbutton.cpp:537
#16 0xb54ec546 in QAbstractButton::mouseReleaseEvent (this=0x9ab2c70, 
    e=0xbfdedcac) at widgets/qabstractbutton.cpp:1116
#17 0xb51d7142 in QWidget::event (this=0x9ab2c70, event=0xbfdedcac)
    at kernel/qwidget.cpp:7169
#18 0xb54ea45e in QAbstractButton::event (this=0x9ab2c70, e=0xbfdedcac)
    at widgets/qabstractbutton.cpp:1078
#19 0xb5599310 in QPushButton::event (this=0x9ab2c70, e=0xbfdedcac)
    at widgets/qpushbutton.cpp:658
#20 0xb517894c in QApplicationPrivate::notify_helper (this=0x965b128, 
    receiver=0x9ab2c70, e=0xbfdedcac) at kernel/qapplication.cpp:3809
#21 0xb5180479 in QApplication::notify (this=0xbfdee3a8, receiver=0x9ab2c70, 
    e=0xbfdedcac) at kernel/qapplication.cpp:3534
#22 0xb5cb06b1 in KApplication::notify (this=0xbfdee3a8, receiver=0x9ab2c70, 
    event=0xbfdedcac)
    at /var/tmp/portage/kde-base/kdelibs-4.1.3-r1/work/kdelibs-4.1.3/kdeui/kernel/kapplication.cpp:311
#23 0xb7ee3ebf in QCoreApplication::notifyInternal (this=0xbfdee3a8, 
    receiver=0x9ab2c70, event=0xbfdedcac) at kernel/qcoreapplication.cpp:593
#24 0xb518190f in QApplicationPrivate::sendMouseEvent (receiver=0x9ab2c70, 
    event=0xbfdedcac, alienWidget=0x9ab2c70, nativeWidget=0x9a2d4d0, 
    buttonDown=0xb5998c60, lastMouseReceiver=@0xb5998c64)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#25 0xb51f02f3 in QETWidget::translateMouseEvent (this=0x9a2d4d0, 
    event=0xbfdee198) at kernel/qapplication_x11.cpp:4048
#26 0xb51eec06 in QApplication::x11ProcessEvent (this=0xbfdee3a8, 
    event=0xbfdee198) at kernel/qapplication_x11.cpp:3044
#27 0xb52172f8 in QEventDispatcherX11::processEvents (this=0x96583f0, flags=
      {i = -1075912136}) at kernel/qeventdispatcher_x11.cpp:134
#28 0xb7ee282a in QEventLoop::processEvents (this=0xbfdee2b0, flags=
      {i = -1075912072}) at kernel/qeventloop.cpp:149
#29 0xb7ee29ea in QEventLoop::exec (this=0xbfdee2b0, flags={i = -1075912008})
    at kernel/qeventloop.cpp:200
#30 0xb7ee5155 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:851
#31 0xb5178677 in QApplication::exec () at kernel/qapplication.cpp:3337
#32 0x0804af2a in main (argc=)
    at /var/tmp/portage/kde-base/kmail-4.1.3/work/kmail-4.1.3/kmail/main.cpp:146
#0  0xb7fd3424 in __kernel_vsyscall ()