Version:           4.0.82+svn819867 (using KDE 4.0.83)
Installed from:    Debian testing/unstable Packages
Compiler:          gcc (Debian 4.3.1-2) 4.3.1 
OS:                Linux

Here are the steps to reproduce:
1. Open a new konqueror window and visit a random page (ex. kde.org)
2. Now visit http://www.csd.uoc.gr/~hy255 in the same tab.
3. On the left frame, click on "Assignments".
4. On the right frame, click on "Assignment 5", then on "x86asm.s" and click to open the file (not save it). It will open in kate part in the right frame.
5. Click back until you reach the page that you initially visited (ex. kde.org)
6. Click forward a few times
7. It crashed! :)

Note that when you click back for the first time, kate part disappears but the previous page is not restored. The right frame is empty. I think this is related to the issue...

Here is the backtrace:
Application: Konqueror (konqueror), signal SIGSEGV
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]            
[New Thread 0x7f2d91fa8780 (LWP 5272)]                   
[KCrash handler]                                         
#5  QString::operator== (this=<value optimized out>, other=@0xc478c0)
    at tools/qstring.cpp:1760                                        
#6  0x00007f2d82c0dd0d in KHTMLPart::restoreState (this=0x12c6c80,   
    stream=<value optimized out>) at /usr/include/qt4/QtCore/qstring.h:378
#7  0x00007f2d91c16e0b in KonqView::restoreHistory (this=0xb3c600)        
    at /tmp/buildd/kdebase-4.0.82+svn819867/apps/konqueror/src/konqview.cpp:859
#8  0x00007f2d91c6617f in KonqMainWindow::slotGoHistoryDelayed (this=0x6a3750) 
    at /tmp/buildd/kdebase-4.0.82+svn819867/apps/konqueror/src/konqmainwindow.cpp:2782
#9  0x00007f2d91c7036d in KonqMainWindow::qt_metacall (this=0x6a3750,                 
    _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>,                      
    _a=0x7fff9a0db580)                                                                
    at /tmp/buildd/kdebase-4.0.82+svn819867/obj-x86_64-linux-gnu/apps/konqueror/src/konqmainwindow.moc:414
#10 0x00007f2d900137e4 in QMetaObject::activate (sender=0xbfea10,                                         
    from_signal_index=<value optimized out>, to_signal_index=4, argv=0x4)                                 
    at kernel/qobject.cpp:3010                                                                            
#11 0x00007f2d90019acf in QSingleShotTimer::timerEvent (this=0xbfea10)                                    
    at kernel/qtimer.cpp:300                                                                              
#12 0x00007f2d9000e0f3 in QObject::event (this=0xbfea10, e=0xc478c0)                                      
    at kernel/qobject.cpp:1105                                                                            
#13 0x00007f2d8f52de5d in QApplicationPrivate::notify_helper (this=0x619940,                              
    receiver=0xbfea10, e=0x7fff9a0dbc50) at kernel/qapplication.cpp:3772                                  
#14 0x00007f2d8f535b2a in QApplication::notify (this=0x7fff9a0dc160,                                      
    receiver=0xbfea10, e=0x7fff9a0dbc50) at kernel/qapplication.cpp:3739                                  
#15 0x00007f2d9095ee5b in KApplication::notify (this=0x7fff9a0dc160,                                      
    receiver=0xbfea10, event=0x7fff9a0dbc50)                                                              
    at /tmp/buildd/kde4libs-4.0.82+svn819867/kdeui/kernel/kapplication.cpp:311                            
#16 0x00007f2d8ffff491 in QCoreApplication::notifyInternal (                                              
    this=0x7fff9a0dc160, receiver=0xbfea10, event=0x7fff9a0dbc50)                                         
    at kernel/qcoreapplication.cpp:587                                                                    
#17 0x00007f2d9002b436 in QTimerInfoList::activateTimers (this=0x61ce50)                                  
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215                               
#18 0x00007f2d9002795d in timerSourceDispatch (source=<value optimized out>)
    at kernel/qeventdispatcher_glib.cpp:166
#19 0x00007f2d8be5f0f2 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#20 0x00007f2d8be62396 in ?? () from /usr/lib/libglib-2.0.so.0
#21 0x00007f2d8be6282f in g_main_context_iteration ()
   from /usr/lib/libglib-2.0.so.0
#22 0x00007f2d900278bf in QEventDispatcherGlib::processEvents (this=0x614b50,
    flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:325
#23 0x00007f2d8f5bf16f in QGuiEventDispatcherGlib::processEvents (
    this=0xc0d8d0, flags=<value optimized out>)
    at kernel/qguieventdispatcher_glib.cpp:204
#24 0x00007f2d8fffdda2 in QEventLoop::processEvents (
    this=<value optimized out>, flags={i = -1710375264})
    at kernel/qeventloop.cpp:149
#25 0x00007f2d8fffdf2d in QEventLoop::exec (this=0x7fff9a0dbee0, flags=
      {i = -1710375184}) at kernel/qeventloop.cpp:200
#26 0x00007f2d900003fd in QCoreApplication::exec ()
    at kernel/qcoreapplication.cpp:845
#27 0x00007f2d91c98da9 in kdemain (argc=<value optimized out>,
    argv=<value optimized out>)
    at /tmp/buildd/kdebase-4.0.82+svn819867/apps/konqueror/src/konqmain.cpp:226
#28 0x00007f2d918a31c4 in __libc_start_main () from /lib/libc.so.6
#29 0x0000000000400629 in _start ()
#0  0x00007f2d9191c241 in nanosleep () from /lib/libc.so.6

PS: I am using konqueror from the debian experimental packages, which are not exactly beta2, but a few revisions earlier (r819867)