there appeared some kind of leak or memory overwrite, or double destruct, can't
track down where it came from, only thing done (to my knowledge) was to rebuild
kde packages due newer dependencies in distro. maybe gcc overoptimizes, but
rebuild with gcc 4.4.2 did not help.

crash happens when kmail send mail window is destructed (you hit send mail
button)

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff6dba027 in DCOPObject::~DCOPObject (this=0xdf03b8, __in_chrg=<value optimized out>) at dcopobject.cpp:81
81          if ( d->m_signalConnections > 0 && client )
(gdb) bt
#0  0x00007ffff6dba027 in DCOPObject::~DCOPObject (this=0xdf03b8, __in_chrg=<value optimized out>) at dcopobject.cpp:81
#1  0x00007ffff77c6a6b in KMComposeWin::~KMComposeWin (this=0xdefd30, __in_chrg=<value optimized out>, __vtt_parm=<value optimized out>) at kmcomposewin.cpp:490
#2  0x00007ffff66b911a in QObject::event(QEvent*) () from /usr/lib64/libqt-mt.so.3
#3  0x00007ffff66ee013 in QWidget::event(QEvent*) () from /usr/lib64/libqt-mt.so.3
#4  0x00007ffff665a865 in QApplication::internalNotify(QObject*, QEvent*) () from /usr/lib64/libqt-mt.so.3
#5  0x00007ffff665b96e in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libqt-mt.so.3
#6  0x00007ffff70aaf28 in KApplication::notify (this=0x7fffffffda10, receiver=0xdefd30, event=0xe72500) at kapplication.cpp:550
#7  0x00007ffff665c263 in QApplication::sendPostedEvents(QObject*, int) () from /usr/lib64/libqt-mt.so.3
#8  0x00007ffff660acad in QEventLoop::processEvents(unsigned int) () from /usr/lib64/libqt-mt.so.3
#9  0x00007ffff6670ba9 in QEventLoop::enterLoop() () from /usr/lib64/libqt-mt.so.3
#10 0x00007ffff6670a32 in QEventLoop::exec() () from /usr/lib64/libqt-mt.so.3
#11 0x00000000004028cc in main (argc=3, argv=<value optimized out>) at main.cpp:110
(gdb) p d
$1 = (DCOPObject::DCOPObjectPrivate *) 0x0
(gdb) p client
$2 = <value optimized out>
(gdb) l
76      }
77
78      DCOPObject::~DCOPObject()
79      {
80          DCOPClient *client = DCOPClient::mainClient();
81          if ( d->m_signalConnections > 0 && client )
82               client->disconnectDCOPSignal( 0, 0, 0, objId(), 0 );
83
84          objMap()->remove(ident);
85          delete d;
(gdb)

--- kdelibs-3.5.10/dcop/dcopobject.cpp~	2005-09-10 11:27:23.000000000 +0300
+++ kdelibs-3.5.10/dcop/dcopobject.cpp	2010-01-30 07:56:50.818689543 +0200
@@ -78,7 +78,7 @@
 DCOPObject::~DCOPObject()
 {
     DCOPClient *client = DCOPClient::mainClient();
-    if ( d->m_signalConnections > 0 && client )
+    if (d && d->m_signalConnections > 0 && client )
          client->disconnectDCOPSignal( 0, 0, 0, objId(), 0 );
 
     objMap()->remove(ident);