Version:           unknown (using KDE 3.5.5, Debian Package 4:3.5.5a.dfsg.1-8 (4.0))
Compiler:          Target: x86_64-linux-gnu
OS:                Linux (x86_64) release 2.6.18-4-amd64

When scrolling through the messages in a folder by continuously holding down the "previous/next message" button (in my case, the shortcuts are Left/Right) Kmail crashes if the folder has at least one encrypted message. 

The way it happens is a dialog asking for the passphrase pops up, and when you hit Esc the dialog closes and Kmail crashes. The crash is easily reproducible. 

I am almost certain that the problem consists in the fact that by the time the dialog asking for the passphrase opens, the message which is selected is not the message which is encrypted (for me, it was 2 or 3 messages further). The crash occurs even if you enter the correct passphrase in the dialog.

(no debugging symbols found)
Using host libthread_db library "/lib/libthread_db.so.1".
(no debugging symbols found)
(...)
[Thread debugging using libthread_db enabled]
[New Thread 47119907434272 (LWP 6294)]
[New Thread 1107310912 (LWP 6315)]
[New Thread 1098918208 (LWP 6314)]
[New Thread 1090525504 (LWP 6313)]
[New Thread 1082132800 (LWP 6312)]
(...)
(no debugging symbols found)
[KCrash handler]
#5  0x00002adaee63263d in KMail::ObjectTreeParser::parseObjectTree ()
   from /usr/lib/libkmailprivate.so
#6  0x00002adaee63a740 in KMReaderWin::parseMsg ()
   from /usr/lib/libkmailprivate.so
#7  0x00002adaee576bf0 in KMReaderWin::displayMessage ()
   from /usr/lib/libkmailprivate.so
#8  0x00002adaee5a70a6 in KMReaderWin::updateReaderWin ()
   from /usr/lib/libkmailprivate.so
#9  0x00002adaee62d438 in KMReaderWin::qt_invoke ()
   from /usr/lib/libkmailprivate.so
#10 0x00002adaef85fc2e in QObject::activate_signal ()
   from /usr/lib/libqt-mt.so.3
#11 0x00002adaef8607be in QObject::activate_signal ()
   from /usr/lib/libqt-mt.so.3
#12 0x00002adaefbcec62 in QTimer::timeout () from /usr/lib/libqt-mt.so.3
#13 0x00002adaef885ff7 in QTimer::event () from /usr/lib/libqt-mt.so.3
#14 0x00002adaef7fb26a in QApplication::internalNotify ()
   from /usr/lib/libqt-mt.so.3
#15 0x00002adaef7fd014 in QApplication::notify () from /usr/lib/libqt-mt.so.3
#16 0x00002adaef1558be in KApplication::notify ()
   from /usr/lib/libkdecore.so.4
#17 0x00002adaef78e802 in QApplication::sendEvent ()
   from /usr/lib/libqt-mt.so.3
#18 0x00002adaef7ee57c in QEventLoop::activateTimers ()
   from /usr/lib/libqt-mt.so.3
#19 0x00002adaef7a2584 in QEventLoop::processEvents ()
   from /usr/lib/libqt-mt.so.3
#20 0x00002adaef8147f6 in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#21 0x00002adaef8145ff in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#22 0x00002adaef7fcd48 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#23 0x000000000040291d in ?? ()
#24 0x00002adaeed42314 in __libc_start_main () from /lib/libc.so.6
#25 0x00000000004026aa in ?? ()
#26 0x00007fffbca123f8 in ?? ()
#27 0x0000000000000000 in ?? ()