Version:           1.9.51 (using 4.00.80 (KDE 4.0.80 >= (KDE 4.1 Beta1), Debian packages)
Compiler:          cc
OS:                Linux (i686) release 2.6.24-1-686

To reproduce the crash: Go to tools, Anti-Spam Wizard, SpamAssassin 3.x (Perl)is detected, Next, click on the blue folder to change directory, and click on the "-" sign next to "Local Folders".

I tried to generate a backtrace, but I wasn't too successful (I installed the debian kdepim-dbg package and followed the ubuntu wiki):

GNU gdb 6.8-debian               
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.           
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"   
and "show warranty" for details.                                             
This GDB was configured as "i486-linux-gnu"...                               
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(gdb) handle SIG33 pass nostop noprint                                       
Signal        Stop      Print   Pass to program Description                  
SIG33         No        No      Yes             Real-time event 33           
(gdb) set pagination 0                                                        
(gdb) run                                                                     
Starting program: /usr/bin/kmail                                              
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[New Thread 0xb4233720 (LWP 11380)]                                           
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kmail(11383) KMail::lockOrDie: oldPid= 11104                                  
kmail(11383) KMKernel::KMKernel:                                              
kmail(11383) KWallet::Wallet::openWallet: Pass a valid window to KWallet::Wallet::openWallet(). 
kmail(11383) KMKernel::init: foldersPath (from config): ' "/home/arnout/Mail" '                 
"/usr/bin/kmail(11383)" Error in thread 3022206752 : "org.freedesktop.DBus.Error.ServiceUnknown - The name org.kde.nepomuk.services.nepomukstorage was not provided by any .service files"                                                                                                
local socket error: QLocalSocket::ServerNotFoundError                                                                                        
"/usr/bin/kmail(11383)" Error in thread 3022206752 : "QLocalSocket::connectToServer: Invalid name"                                           
kmail(11383) <unnamed>::GlobalModelContainer::init: Failed to connect to Nepomuk server via local socket "/home/arnout/.kde/share/apps/nepomuk/socket"                                                                                                                                    
kmail(11383) KMKernel::identityManager:                                                                                                      
kmail(11383) KMFilterMgr::KMFilterMgr: pPopFilter set                                                                                        
kmail(11383) KWallet::Wallet::openWallet: Pass a valid window to KWallet::Wallet::openWallet().                                              
kmail(11383) KMFolderMaildir::createIndexFromContents: Creating index for "/home/arnout/.kde/share/apps/kmail/autosave"                      
kmail(11383) KMFolderMaildir::createIndexFromContents: Creating index for "/home/arnout/.kde/share/apps/kmail/autosave"                      
kmail(11383) KMailApplication::newInstance:                                                                                                  
kmail(11383) KMKernel::openReader:                                                                                                           

Program exited normally.
(gdb) kmail(11383) KMReaderWin::setMsg: ( 281130 , last 0 ) "Re: PR" "Torren Carlson" , readyToShow true
kmail(11383) KMReaderWin::overrideCodec:  mOverrideEncoding == ' "" '                                   
kmail(11383) KMail::Vacation::Vacation: Vacation: found url " "" "                                      
kmail(11383) KMReaderWin::overrideCodec:  mOverrideEncoding == ' "" '                                   
kmail(11383) partNode::fillMimePartTree:       Inserting one item into MimePartTree                     
kmail(11383) partNode::fillMimePartTree:                 Content-Type: "Text/Plain"                     
kmail(11383) KMail::ObjectTreeParser::parseObjectTree: node OK,  showOnlyOneMimePart:  FALSE            
kmail(11383) loadPlugins: BodyPartFormatterFactory: found 4  plugins.                                   
kmail(11383) insertBodyPartFormatter: BodyPartFormatterFactory: overwriting previously registered formatter for " application / octet-stream "
kmail(11383) insertBodyPartFormatter: BodyPartFormatterFactory: instantiating new Subtype Registry for " text "
kmail(11383) <unnamed>::UrlHandler::UrlHandler: UrlHandler() (iCalendar)
kmail(11383) KMReaderWin::overrideCodec:  mOverrideEncoding == ' "" '
kmail(11383) KMReaderWin::parseMsg: Finished parsing and displaying of message.
kmail(11383) KMail::AntiSpamWizard::checkToolAvailability: Testing for server pattern: "gmx"
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "crm -v | grep "CRM114""
/bin/sh: crm: command not found
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "bsfilter --help > /dev/null"
/bin/sh: bsfilter: command not found
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "bogofilter -V"
/bin/sh: bogofilter: command not found
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "echo "From: test" | spamc -x && spamassassin -V | grep "SpamAssassin version 3""
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "spamassassin -V | grep "SpamAssassin version 3""
SpamAssassin version 3.2.4
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "spamassassin -V | grep "SpamAssassin version 2""
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "$HOME/.annoyance-filter/annoyance-filter --version"
/bin/sh: /home/arnout/.annoyance-filter/annoyance-filter: No such file or directory
kmail(11383) KMail::AntiSpamWizard::checkForProgram: Testing for executable: "sb_filter.py -h"
/bin/sh: sb_filter.py: command not found
*** KMail got signal 11 (Crashing)
KCrash: Application 'kmail' crashing...
Unable to start Dr. Konqi

(gdb) backtrace full
No stack.
(gdb) info registers
The program has no registers now.
(gdb) thread apply all backtrace
No registers.
(gdb) quit