Version:           3.5.8 (using KDE 3.5.8, Kubuntu (gutsy) 4:3.5.8-0ubuntu3.1)
OS:                Linux (i686) release 2.6.22-14-generic

Download the update of flashplayer (culprit version 9.0.r115 at time of writing) from:
 http://fpdownload.macromedia.com/get/flashplayer/current/install_flash_player_9_linux.tar.gz

# tar xvf install_flash_player_9_linux.tar.gz
# cd install_flash_player_9_linux/
# ./flashplayer-installer

Install to ~/.mozilla/plugins and logoff.

To check that install went properly, open about:plugins in konqueror and firefox; both applications report that the installation was OK:
Shockwave Flash Shockwave Flash 9.0 r115 libflashplayer.so
When konqueror is started from a konsole and then opening a swf file in a new tab:

----snip----
# konqueror

 (process:10052): Gtk-CRITICAL **: gtk_clipboard_get_for_display: assertion `display != NULL' failed
 Adobe Flash Player: gtk_clipboard_get(GDK_SELECTION_PRIMARY); failed. Trying to call gtk_init(0,0);
----snip----

Then closing tab:

----snip----
X Error: BadWindow (invalid Window parameter) 3
   Major opcode: 10
   Minor opcode: 0
   Resource id: 0x2a00008
 X Error: BadWindow (invalid Window parameter) 3
   Major opcode: 7
   Minor opcode: 0
   Resource id: 0x2a00008
 X Error: BadWindow (invalid Window parameter) 3
   Major opcode: 25
   Minor opcode: 0
   Resource id: 0x2a00008
 KCrash: Application 'nspluginviewer' crashing...
----snip----

Then produces the following crash handler backtrace;

----snip----
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1208121664 (LWP 16324)]
[New Thread -1267860592 (LWP 16361)]
[New Thread -1259467888 (LWP 16334)]
[New Thread -1251075184 (LWP 16333)]
[New Thread -1242682480 (LWP 16332)]
[KCrash handler]
#6  0x4f89d1b7 in XtRemoveTimeOut () from /usr/lib/libXt.so.6
#7  0xb751ddb1 in ?? () from /home/wepiha/.mozilla/plugins/libflashplayer.so
#8  0xb7513338 in ?? () from /home/wepiha/.mozilla/plugins/libflashplayer.so
#9  0xb750c181 in ?? () from /home/wepiha/.mozilla/plugins/libflashplayer.so
#10 0xb7510937 in ?? () from /home/wepiha/.mozilla/plugins/libflashplayer.so
#11 0x080ca9a0 in ?? ()
#12 0xbfd2c758 in ?? ()
#13 0xbfd2c728 in ?? ()
#14 0x42a67d81 in operator delete () from /usr/lib/libstdc++.so.6
#15 0x0805b62f in NSPluginInstance::destroy (this=0x80caf20)
    at /build/buildd/kdebase-3.5.8/./nsplugins/viewer/nsplugin.cpp:710
#16 0x0805d78d in ~NSPluginInstance (this=0x80caf20)
    at /build/buildd/kdebase-3.5.8/./nsplugins/viewer/nsplugin.cpp:672
#17 0x4ff4fe50 in QGList::remove () from /usr/lib/libqt-mt.so.3
#18 0x0805652f in NSPluginClass::timer (this=0x80b0990)
    at /usr/share/qt3/include/qptrlist.h:85
#19 0x080565c1 in NSPluginInstance::shutdown (this=0x80caf20)
    at /build/buildd/kdebase-3.5.8/./nsplugins/viewer/nsplugin.cpp:740
#20 0x080593b9 in NSPluginInstanceIface::process (this=0x80cb04c,
    fun=@0xbfd2caa4, data=@0xbfd2ca9c, replyType=@0xbfd2ca94,
    replyData=@0xbfd2ca8c) at NSPluginClassIface_skel.cpp:172
#21 0x4139d6b7 in DCOPClient::receive () from /usr/lib/libDCOP.so.4
#22 0x4139ea14 in ?? () from /usr/lib/libDCOP.so.4
#23 0x080a5110 in ?? ()
#24 0xbfd2cab4 in ?? ()
#25 0xbfd2caac in ?? ()
#26 0xbfd2caa4 in ?? ()
#27 0xbfd2ca9c in ?? ()
#28 0xbfd2ca94 in ?? ()
#29 0xbfd2ca8c in ?? ()
#30 0x4ff511fe in QGListIteratorList::remove () from /usr/lib/libqt-mt.so.3
#31 0x4139f535 in ?? () from /usr/lib/libDCOP.so.4
#32 0xbfd2cb68 in ?? ()
#33 0x00000001 in ?? ()
#34 0x080f2e90 in ?? ()
#35 0x080b68d0 in ?? ()
#36 0xbfd2cb38 in ?? ()
#37 0x4264bc84 in read () from /lib/tls/i686/cmov/libc.so.6
#38 0xb7ffae38 in read () from /usr/lib/libartsdsp.so.0
#39 0x413af860 in KDE_IceProcessMessages () from /usr/lib/libDCOP.so.4
#40 0x41395ba3 in DCOPClient::processSocketData () from /usr/lib/libDCOP.so.4
#41 0x4139f139 in DCOPClient::qt_invoke () from /usr/lib/libDCOP.so.4
#42 0x4fc53e53 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#43 0x4fc5476a in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#44 0x4ffe0c43 in QSocketNotifier::activated () from /usr/lib/libqt-mt.so.3
#45 0x4fc76a2e in QSocketNotifier::event () from /usr/lib/libqt-mt.so.3
#46 0x4fbeb0b0 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#47 0x4fbecedf in QApplication::notify () from /usr/lib/libqt-mt.so.3
#48 0x412fde82 in KApplication::notify () from /usr/lib/libkdecore.so.4
#49 0x4fb7d7c9 in QApplication::sendEvent () from /usr/lib/libqt-mt.so.3
#50 0x4fbdd4a9 in QEventLoop::activateSocketNotifiers ()
   from /usr/lib/libqt-mt.so.3
#51 0x080557d6 in QXtEventLoop::processEvents (this=0xbfd2d1c0,
    flags=<value optimized out>)
    at /build/buildd/kdebase-3.5.8/./nsplugins/viewer/qxteventloop.cpp:462
#52 0x4fc0578e in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#53 0x4fc0559e in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#54 0x4fbecc59 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#55 0x08059da5 in main (argc=134620368, argv=0x0)
    at /build/buildd/kdebase-3.5.8/./nsplugins/viewer/viewer.cpp:305
----snip----