Version:           4.0.0 (using KDE Devel)
Installed from:    Compiled sources
Compiler:          gcc 4.1.2 
OS:                Linux

I am not sure if it does this with only one tab but with multiple tabs open if you click the close button on a website konqueror crashes, here is the back trace:
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1208801584 (LWP 31891)]
[KCrash handler]
#6  0x00229812 in KParts::ReadOnlyPart::d_func (this=0x0)
    at /home/ethanw/kde/src/KDE/kdelibs/kparts/part.h:468
#7  0x00226574 in KParts::ReadOnlyPart::url (this=0x0)
    at /home/ethanw/kde/src/KDE/kdelibs/kparts/part.cpp:459
#8  0x0013f449 in KonqView::updateHistoryEntry (this=0xbe02b70, 
    saveLocationBarURL=true)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqview.cpp:744
#9  0x0013fa89 in KonqView::saveConfig (this=0xbe02b70, config=@0xc386cd4, 
    prefix=@0xbffb7094, options=@0xbffb7090)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqview.cpp:1373
#10 0x00153a26 in KonqFrame::saveConfig (this=0xb7cbb08, config=@0xc386cd4, 
    prefix=@0xbffb7094, options=@0xbffb7090, docContainer=0x0)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqframe.cpp:80
#11 0x001726d4 in KonqMainWindow::slotAddClosedUrl (this=0x9faa5d8, 
    tab=0xb7cbb1c)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqmainwindow.cpp:5306
#12 0x00190de0 in KonqMainWindow::qt_metacall (this=0x9faa5d8, 
    _c=QMetaObject::InvokeMetaMethod, _id=37, _a=0xbffb7640)
    at /home/ethanw/kde/build/KDE/kdebase/apps/konqueror/src/konqmainwindow.moc:345
#13 0x00e76331 in QMetaObject::activate (sender=0x9fb25e0, 
    from_signal_index=10, to_signal_index=10, argv=<value optimized out>)
    at kernel/qobject.cpp:3087
#14 0x00e76e45 in QMetaObject::activate (sender=0x9fb25e0, m=0x1c6488, 
    local_signal_index=0, argv=0xbffb7640) at kernel/qobject.cpp:3149
#15 0x00147177 in KonqViewManager::aboutToRemoveTab (this=0x9fb25e0, 
    _t1=0xb7cbb1c)
    at /home/ethanw/kde/build/KDE/kdebase/apps/konqueror/src/konqviewmanager.moc:100
#16 0x0014c836 in KonqViewManager::removeTab (this=0x9fb25e0, 
    currentFrame=0xb7cbb1c)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqviewmanager.cpp:350
#17 0x0014ceb9 in KonqViewManager::removeView (this=0x9fb25e0, view=0xbe02b70)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqviewmanager.cpp:529
#18 0x0014d402 in KonqViewManager::removePart (this=0x9fb25e0, part=0xbe02d18)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqviewmanager.cpp:571
#19 0x00228c33 in ~Part (this=0xbe02d18, __vtt_parm=0x5b835e8)
    at /home/ethanw/kde/src/KDE/kdelibs/kparts/part.cpp:204
#20 0x00228ec5 in ~ReadOnlyPart (this=0xbe02d18, __vtt_parm=0x5b835e4)
    at /home/ethanw/kde/src/KDE/kdelibs/kparts/part.cpp:455
#21 0x05858617 in ~KHTMLPart (this=0xbe02d18)
    at /home/ethanw/kde/src/KDE/kdelibs/khtml/khtml_part.cpp:527
#22 0x00e731ca in QObject::event (this=0xbe02d18, e=0xf0)
    at kernel/qobject.cpp:1114
#23 0x00fe9dd4 in QApplicationPrivate::notify_helper (this=0x9efc178, 
    receiver=0xbe02d18, e=0xa9d3930) at kernel/qapplication.cpp:3556
#24 0x00fed64c in QApplication::notify (this=0xbffb8178, receiver=0xbe02d18, 
    e=0xa9d3930) at kernel/qapplication.cpp:3115
#25 0x0092ee5b in KApplication::notify (this=0xbffb8178, receiver=0xbe02d18, 
    event=0xa9d3930)
    at /home/ethanw/kde/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:314
#26 0x00e6236b in QCoreApplication::notifyInternal (this=0xbffb8178, 
    receiver=0xbe02d18, event=0xa9d3930) at kernel/qcoreapplication.cpp:530
#27 0x00e636bb in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, 
    event_type=0, data=0x9eeff50)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:200
#28 0x00e639ea in QCoreApplication::sendPostedEvents (receiver=0x0, 
    event_type=-1) at kernel/qcoreapplication.cpp:1001
#29 0x00e8431c in postEventSourceDispatch (s=0x9eff430)
    at kernel/qeventdispatcher_glib.cpp:207
#30 0x06dcc10c in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#31 0x06dcf54f in ?? () from /lib/libglib-2.0.so.0
#32 0x06dcfab5 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#33 0x00e84643 in QEventDispatcherGlib::processEvents (this=0x9efc070, 
    flags=@0xbffb7f38) at kernel/qeventdispatcher_glib.cpp:338
#34 0x01064f3a in QGuiEventDispatcherGlib::processEvents (this=0x9efc070, 
    flags=@0xbffb7f68) at kernel/qguieventdispatcher_glib.cpp:191
#35 0x00e61976 in QEventLoop::processEvents (this=0xbffb7fc0, 
    flags=@0xbffb7f98) at kernel/qeventloop.cpp:140
#36 0x00e61a70 in QEventLoop::exec (this=0xbffb7fc0, flags=@0xbffb7fc8)
    at kernel/qeventloop.cpp:182
#37 0x00e63a8e in QCoreApplication::exec () at kernel/qcoreapplication.cpp:759
#38 0x00fe927a in QApplication::exec () at kernel/qapplication.cpp:3053
#39 0x001b44e6 in kdemain (argc=2, argv=0xbffb84e4)
    at /home/ethanw/kde/src/KDE/kdebase/apps/konqueror/src/konqmain.cpp:218
#40 0x080487d3 in main (argc=)
    at /home/ethanw/kde/build/KDE/kdebase/apps/konqueror/src/konqueror_dummy.cpp:3
#0  0x00110402 in __kernel_vsyscall ()