Version:            (using Devel)
Compiler:          gcc 4.4.1 
OS:                Linux
Installed from:    Compiled sources

KDE SC version : 4.4b2 on Kubuntu Lucid alpha1
I have nspluginviewer installed via the flashplugin-installer package (v. 10.0.42.34ubuntu1 from the Lucid repos).

about:plugins gives that :

Shockwave Flash  Shockwave Flash 10.0 r42  flashplugin-alternative.so
  application/x-shockwave-flash - Shockwave Flash (swf)
application/futuresplash - FutureSplash Player (spl)


What happened : I was browsing with konqueror on this page : http://braquo.canalplus.fr/annexes/la-serie
This website contains quite a lot of flash animations, and on this page in particular there is at the bottom an animation (in red) spanning over all the window's width.
The window was maximised.
I then resized the window and nspluginviewer crashed with the following backtrace. I can reproduce this crash on a 100%-basis.
However I could't find out how to install the debugging packages for /usr/lib/firefox/plugins/flashplugin-alternative.so

Backtrace :

Application: nspluginviewer (nspluginviewer), signal: Segmentation fault
[Current thread is 1 (Thread 0xb77e5700 (LWP 17265))]

Thread 3 (Thread 0xb51b5b70 (LWP 17269)):
#0  0x00407422 in __kernel_vsyscall ()
#1  0x007c2e05 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0x003798dd in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0x01adf79f in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#4  0x01c127ff in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#5  0x01adfc5d in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#6  0x007be80e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0x0036c93e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 2 (Thread 0xb49b4b70 (LWP 17270)):
#0  0x00407422 in __kernel_vsyscall ()
#1  0x007c2e05 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0x003798dd in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0x01adf79f in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#4  0x01c127ff in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#5  0x01adfc5d in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#6  0x007be80e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0x0036c93e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb77e5700 (LWP 17265)):
[KCrash Handler]
#6  g_data_set_internal (datalist=0x8393030, key_id=50, data=0x0, destroy_func=0) at /build/buildd/glib2.0-2.23.0/glib/gdataset.c:216
#7  IA__g_datalist_id_set_data_full (datalist=0x8393030, key_id=50, data=0x0, destroy_func=0) at /build/buildd/glib2.0-2.23.0/glib/gdataset.c:362
#8  0x02c4df97 in g_object_real_dispose (object=0x8393028) at /build/buildd/glib2.0-2.23.0/gobject/gobject.c:766
#9  0x026c8bdd in gtk_object_dispose (gobject=0x8393028) at /build/buildd/gtk+2.0-2.19.1/gtk/gtkobject.c:426
#10 0x027eba01 in gtk_widget_dispose (object=0x8393028) at /build/buildd/gtk+2.0-2.19.1/gtk/gtkwidget.c:8552
#11 0x027fa3ec in gtk_window_dispose (object=0x8393028) at /build/buildd/gtk+2.0-2.19.1/gtk/gtkwindow.c:2151
#12 0x02c4e2b0 in IA__g_object_unref (_object=0x8393028) at /build/buildd/glib2.0-2.23.0/gobject/gobject.c:2441
#13 0x01ad29a2 in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#14 0x01ac8571 in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#15 0x01accda4 in ?? () from /usr/lib/firefox/plugins/flashplugin-alternative.so
#16 0x080512d9 in NSPluginInstance::NPSetWindow (this=0x8393030, window=0xbffd5178) at ../../../../apps/nsplugins/viewer/nsplugin.cpp:1031
#17 0x0805d5d0 in PluginHost::setupPluginWindow (this=0x838acf0, plugin=0x838a9e8, winID=0x2baf308, width=828, height=475) at ../../../../apps/nsplugins/viewer/pluginhost.cpp:54
#18 0x0805cab1 in PluginHostXEmbed::resizePlugin (this=0x838acf0, pluginWinId=50331651, w=828, h=475) at ../../../../apps/nsplugins/viewer/pluginhost_xembed.cpp:51
#19 0x08050875 in NSPluginInstance::resizePlugin (this=0x838a9e8, clientWinId=50331651, w=828, h=475) at ../../../../apps/nsplugins/viewer/nsplugin.cpp:949
#20 0x0805dd24 in InstanceAdaptor::resizePlugin (this=0x8388200, _c=QMetaObject::InvokeMetaMethod, _id=7, _a=0xbffd53ec) at instanceadaptor.cpp:57
#21 InstanceAdaptor::qt_metacall (this=0x8388200, _c=QMetaObject::InvokeMetaMethod, _id=7, _a=0xbffd53ec) at instanceadaptor.moc:102
#22 0x001328a4 in QDBusConnectionPrivate::deliverCall (this=0x82ad490, object=0x8388200, msg=..., metaTypes=..., slotIdx=7) at qdbusintegrator.cpp:904
#23 0x00133b9f in QDBusConnectionPrivate::activateCall (this=0x82ad490, object=0x8388200, flags=273, msg=...) at qdbusintegrator.cpp:809
#24 0x00134640 in QDBusConnectionPrivate::activateObject (this=0x82ad490, node=..., msg=..., pathStartPos=11) at qdbusintegrator.cpp:1368
#25 0x001348da in QDBusActivateObjectEvent::placeMetaCall (this=0x83e1cd8) at qdbusintegrator.cpp:1481
#26 0x015da0ee in QObject::event (this=0x838a9e8, e=0x83e1cd8) at kernel/qobject.cpp:1260
#27 0x033ed1dc in QApplicationPrivate::notify_helper (this=0x8256218, receiver=0x838a9e8, e=0x83e1cd8) at kernel/qapplication.cpp:4242
#28 0x033f3e37 in QApplication::notify (this=0xbffd5e88, receiver=0x838a9e8, e=0x83e1cd8) at kernel/qapplication.cpp:3661
#29 0x0102d2fa in KApplication::notify (this=0xbffd5e88, receiver=0x838a9e8, event=0x83e1cd8) at ../../kdeui/kernel/kapplication.cpp:302
#30 0x015c96fb in QCoreApplication::notifyInternal (this=0xbffd5e88, receiver=0x838a9e8, event=0x83e1cd8) at kernel/qcoreapplication.cpp:704
#31 0x015cc133 in QCoreApplication::sendEvent (receiver=0x0, event_type=0, data=0x8241080) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#32 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x8241080) at kernel/qcoreapplication.cpp:1345
#33 0x015cc29d in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1238
#34 0x015f58ff in QCoreApplication::sendPostedEvents (s=0x8258720) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#35 postEventSourceDispatch (s=0x8258720) at kernel/qeventdispatcher_glib.cpp:276
#36 0x00221fd8 in g_main_dispatch (context=0x8258698) at /build/buildd/glib2.0-2.23.0/glib/gmain.c:1960
#37 IA__g_main_context_dispatch (context=0x8258698) at /build/buildd/glib2.0-2.23.0/glib/gmain.c:2513
#38 0x00225880 in g_main_context_iterate (context=0x8258698, block=<value optimized out>, dispatch=1, self=0x8243948) at /build/buildd/glib2.0-2.23.0/glib/gmain.c:2591
#39 0x002259b3 in IA__g_main_context_iteration (context=0x8258698, may_block=1) at /build/buildd/glib2.0-2.23.0/glib/gmain.c:2654
#40 0x015f53f5 in QEventDispatcherGlib::processEvents (this=0x82561b8, flags=...) at kernel/qeventdispatcher_glib.cpp:407
#41 0x034aaba5 in QGuiEventDispatcherGlib::processEvents (this=0x82561b8, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#42 0x015c7d19 in QEventLoop::processEvents (this=0xbffd5cf4, flags=) at kernel/qeventloop.cpp:149
#43 0x015c816a in QEventLoop::exec (this=0xbffd5cf4, flags=...) at kernel/qeventloop.cpp:201
#44 0x015cc35f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#45 0x033ed277 in QApplication::exec () at kernel/qapplication.cpp:3570
#46 0x0805bd55 in main (argc=3, argv=0xbffd5fc4) at ../../../../apps/nsplugins/viewer/viewer.cpp:144