Version:           1.10.92 (using Devel)
OS:                Linux
Installed from:    Compiled sources

Originally file here:
https://bugs.launchpad.net/ubuntu/+source/kdepim/+bug/311521/

Many of the times, when I delete a thread, I'm getting a crash. Here is the tail log of $ gdb --args kmail --nofork

[Thread 0x7f11859a8950 (LWP 3477) exited]
[New Thread 0x7f11859a8950 (LWP 6572)]
QGpgMEProgressTokenMapper::map( "-&24" 63 )
QGpgMEProgressTokenMapper::map( "-&24" 63 )
QGpgMEProgressTokenMapper::map( "-" 63 )
QGpgMEProgressTokenMapper::map( "-" 63 )
kmail(30646) Kleo::_detail::ThreadedJobMixin<T_base, T_result>::slotFinished:
kmail(30646) Kleo::_detail::ThreadedJobMixin<T_base, T_result>::doEmitResult:
kmail(30646) Kleo::_detail::ThreadedJobMixin<T_base, T_result>::slotFinished: end
ASSERT: "dyingMessage->isViewable()" in file /build/buildd/kdepim-4.1.85/kmail/messagelistview/core/model.cpp, line 2921

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7f11a0967750 (LWP 30646)]
0x00007f11970a0fa5 in raise () from /lib/libc.so.6
(gdb) quit

$ apt-cache show kmail
Package: kmail
Priority: optional
Section: mail
Installed-Size: 10176
Maintainer: Kubuntu Developers <kubuntu-devel@lists.ubuntu.com>
Original-Maintainer: Debian Qt/KDE Maintainers <debian-qt-kde@lists.debian.org>
Architecture: amd64
Source: kdepim
Version: 4:4.1.85-0ubuntu1

$ apt-cache show kdepim
Package: kdepim
Priority: optional
Section: kde
Installed-Size: 84
Maintainer: Kubuntu Developers <kubuntu-devel@lists.ubuntu.com>
Original-Maintainer: Debian Qt/KDE Maintainers <debian-qt-kde@lists.debian.org>
Architecture: all
Version: 4:4.1.85-0ubuntu1

$ kmail --version
Qt: 4.4.3
KDE: 4.1.85 (KDE 4.1.85 (KDE 4.2 Beta2))
KMail: 1.10.92

$ dpkg -S libc.so.6
libc6-i386: /lib32/libc.so.6
libc6: /lib/libc.so.6

$ apt-cache show libc6
Package: libc6
Priority: required
Section: base
Installed-Size: 11452
Maintainer: Ubuntu Core developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: GNU Libc Maintainers <debian-glibc@lists.debian.org>
Architecture: amd64
Source: glibc
Version: 2.9-0ubuntu5
Provides: glibc-2.8-1

ProblemType: Bug
Architecture: amd64
Dependencies:

DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia
Package: kdepim None [modified: /var/lib/dpkg/info/kdepim.list]
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 PATH: custom, no user
 LANG=en_US.UTF-8
SourcePackage: kdepim
Uname: Linux 2.6.28-3-generic x86_64

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x7f0f14589750 (LWP 11800)]
0x00007f0f0acc2fa5 in raise () from /lib/libc.so.6
(gdb) bt
#0 0x00007f0f0acc2fa5 in raise () from /lib/libc.so.6
#1 0x00007f0f0acc4b13 in abort () from /lib/libc.so.6
#2 0x00007f0f0ba83725 in qt_message_output () from /usr/lib/libQtCore.so.4
#3 0x00007f0f0ba8386d in qFatal () from /usr/lib/libQtCore.so.4
#4 0x00007f0f1348fa27 in KMail::MessageListView::Core::Model::viewItemJobStepInternalForJobPass1Cleanup (this=0x229bc10, job=0x2f5fb20,
    tStart=@0x7fff1c5d7780) at /build/buildd/kdepim-4.1.85/kmail/messagelistview/core/model.cpp:2921
#5 0x00007f0f1349283d in KMail::MessageListView::Core::Model::viewItemJobStepInternalForJob (this=0x229bc10, job=0x2e18,
    tStart=@0x7fff1c5d7780) at /build/buildd/kdepim-4.1.85/kmail/messagelistview/core/model.cpp:3301
#6 0x00007f0f13492e75 in KMail::MessageListView::Core::Model::viewItemJobStepInternal (this=0x229bc10)
    at /build/buildd/kdepim-4.1.85/kmail/messagelistview/core/model.cpp:3503
#7 0x00007f0f13493da8 in KMail::MessageListView::Core::Model::viewItemJobStep (this=0x229bc10)
    at /build/buildd/kdepim-4.1.85/kmail/messagelistview/core/model.cpp:3662
#8 0x00007f0f1303a2c8 in KMail::MessageListView::Core::Model::qt_metacall (this=0x229bc10, _c=QMetaObject::InvokeMetaMethod,
    _id=<value optimized out>, _a=0x7fff1c5d7ab0) at /build/buildd/kdepim-4.1.85/obj-x86_64-linux-gnu/kmail/moc_model.cpp:75
#9 0x00007f0f0bb88154 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#10 0x00007f0f0bb82a63 in QObject::event () from /usr/lib/libQtCore.so.4
#11 0x00007f0f0c297bfd in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#12 0x00007f0f0c29f9ba in QApplication::notify () from /usr/lib/libQtGui.so.4
#13 0x00007f0f13fc5e7b in KApplication::notify () from /usr/lib/libkdeui.so.5
#14 0x00007f0f0bb73d81 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#15 0x00007f0f0bb9fac6 in ?? () from /usr/lib/libQtCore.so.4
#16 0x00007f0f0bb9c22d in ?? () from /usr/lib/libQtCore.so.4
#17 0x00007f0f0589a1ab in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#18 0x00007f0f0589d96d in ?? () from /usr/lib/libglib-2.0.so.0
#19 0x00007f0f0589db2b in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#20 0x00007f0f0bb9c18f in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#21 0x00007f0f0c329adf in ?? () from /usr/lib/libQtGui.so.4
#22 0x00007f0f0bb726a2 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#23 0x00007f0f0bb7282d in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#24 0x00007f0f0bb74cdd in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#25 0x000000000040324b in main (argc=<value optimized out>, argv=<value optimized out>) at /build/buildd/kdepim-4.1.85/kmail/main.cpp:146
(gdb)

I've noticed that it only happens when deleting with a custom keyboard shortcut ctrl+d.
Using the toolbar icon, or the default shorcut ctrl+DELETE doesnt seem to make it crash.