Version:            (using KDE 3.5.8)
Installed from:    FreeBSD Ports
Compiler:          gcc version 3.4.6 [FreeBSD] 20060305 
OS:                FreeBSD

I think this is a stack overflow as I have over 65000 stack frames.  I won't cut and paste all of it (I don't have the patience).  Here are the first few frames from the top of stack:

(gdb) where
#0  0x2a1322ac in QListViewItem::listView () from /usr/local/lib/libqt-mt.so.3
#1  0x2a132528 in QListViewItem::enforceSortOrder ()
   from /usr/local/lib/libqt-mt.so.3
#2  0x2a132ef2 in QListViewItem::firstChild ()
   from /usr/local/lib/libqt-mt.so.3
#3  0x2a13dfa8 in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3
#4  0x2a13dfcc in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3
#5  0x2a13dfcc in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3
#6  0x2a13dfcc in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3
...

For the bottom of the stack I used frame to find the bottom and then walked up until I ran into QListViewItemIterator::operator++ ():

#65216 0x0804a686 in main ()
(gdb) down
#65215 0x29fe8f0f in QApplication::exec () from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65214 0x2a000436 in QEventLoop::exec () from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65213 0x2a0004e2 in QEventLoop::enterLoop () from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65212 0x29f9397c in QEventLoop::processEvents ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65211 0x29fdd584 in QEventLoop::activateSocketNotifiers ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65210 0x29a88b38 in KApplication::notify ()
   from /usr/local/lib/libkdecore.so.6
(gdb) down
#65209 0x29fe9efc in QApplication::notify () from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65208 0x29fe9d5f in QApplication::internalNotify ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65207 0x2a06aeff in QSocketNotifier::event ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65206 0x2a3a5170 in QSocketNotifier::activated ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65205 0x2a04eada in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65204 0x2a04e514 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65203 0x29474c58 in KIO::Slave::qt_invoke () from /usr/local/lib/libkio.so.6
(gdb) down
#65202 0x2947489b in KIO::Slave::gotInput () from /usr/local/lib/libkio.so.6
(gdb) down
#65201 0x29478b13 in KIO::SlaveInterface::dispatch ()
   from /usr/local/lib/libkio.so.6
(gdb) down
#65200 0x2947a09c in KIO::SlaveInterface::dispatch ()
   from /usr/local/lib/libkio.so.6
(gdb) down
#65199 0x2947738c in KIO::SlaveInterface::finished ()
   from /usr/local/lib/libkio.so.6
(gdb) down
#65198 0x2a04ec32 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65197 0x2a04e514 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb) down
#65196 0x294a461b in KIO::ListJob::qt_invoke () from /usr/local/lib/libkio.so.6
(gdb) down
#65195 0x29491830 in KIO::ListJob::slotFinished ()
   from /usr/local/lib/libkio.so.6
(gdb)
#65194 0x2948c5cc in KIO::SimpleJob::slotFinished ()
   from /usr/local/lib/libkio.so.6
(gdb)
#65193 0x29489f5c in KIO::Job::emitResult () from /usr/local/lib/libkio.so.6
(gdb)
#65192 0x29489ebd in KIO::Job::result () from /usr/local/lib/libkio.so.6
(gdb)
#65191 0x2a04e514 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65190 0x2838809f in KMFolderImap::qt_invoke ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65189 0x28385739 in KMFolderImap::slotListFolderResult ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65188 0x28377a87 in KMFolderImap::finishMailCheck ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65187 0x283779cf in KMFolderImap::folderComplete ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65186 0x2a04e49d in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65185 0x28461eb1 in KMMainWidget::qt_invoke ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65184 0x2845206d in KMMainWidget::folderSelected ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65183 0x28451c18 in KMMainWidget::folderSelected ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65182 0x282900c9 in KMHeaders::setFolder ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65181 0x28289996 in KMHeaders::updateMessageList ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65180 0x282823cc in KMHeaders::messageListUpdated ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65179 0x2a04ec32 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65178 0x2a04e514 in QObject::activate_signal ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65177 0x284d1744 in KMail::HeaderListQuickSearch::qt_invoke ()
   from /usr/local/lib/libkmailprivate.so
(gdb)
#65176 0x2994eabb in KListViewSearchLine::qt_invoke ()
   from /usr/local/lib/libkdeui.so.6
(gdb)
#65175 0x2994cd84 in KListViewSearchLine::updateSearch ()
   from /usr/local/lib/libkdeui.so.6
(gdb)
#65174 0x2a13e199 in QListViewItemIterator::QListViewItemIterator ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65173 0x2a13dfcc in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3
(gdb)
#65172 0x2a13dfcc in QListViewItemIterator::operator++ ()
   from /usr/local/lib/libqt-mt.so.3

My guess is the real issue is in qt itself and the implementation of QListViewItemIterator::operator++ () and its apparent use of recursion.  I am using qt-3.3.8 (+ KDE patches) built from FreeBSD ports.  The QListViewItemIterator::operator++() routine from my build looks like this:

QListViewItemIterator &QListViewItemIterator::operator++()
{
    if ( !curr )
        return *this;

    QListViewItem *item = curr->firstChild();
    if ( !item ) {
        while ( (item = curr->nextSibling()) == 0  ) {
            curr = curr->parent();
            if ( curr == 0 )
                break;
        }
    }
    curr = item;
    // if the next one doesn't match the flags we try one more ahead
    if ( curr && !matchesFlags( curr ) )
        ++( *this );
    return *this;
}

I think the '++( *this)' is the source of the recursion.  Perhaps this could be done via an iterative algorithm instead?