After using the menu editor to add opera to the menu, I was able to add the application to the file association, by selecting it from the menu tree instead of entering the command.

Hello,

Thanks for your report. It sounds as if you are able to reproduce the crash. So could you please have a look at http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports, try to install the debugging packages for your distribution and post a more detailed backtrace?

I ran systemsettings from konsole, which produced this output ...
[dave@hodgins ~]$ findServiceByDesktopPath: MissingMimesAdd-2.desktop not found
ASSERT: "service" in file /home/mandrake/rpm/BUILD/kdebase-4.1.2/apps/konqueror/settings/filetypes/kservicelistwidget.cpp, line 247
KCrash: Application 'systemsettings' crashing...
sock_file=/home/dave/.kde4/socket-hodgins.homeip.net/kdeinit4__0

Here's the backtrace with the debug versions installed.  Note that the application I'm adding is a command (bash script), that does not have any .desktop files, etc., associated with it.

Application: System Settings (systemsettings), signal SIGABRT
(no debugging symbols found)
[Thread debugging using libthread_db enabled]
[New Thread 0xb8020af0 (LWP 11687)]
[KCrash handler]
#6  0xffffe424 in __kernel_vsyscall ()
#7  0x4ed33d90 in raise (sig=<value optimized out>)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#8  0x4ed357f8 in abort () at abort.c:88
#9  0x4e083ae5 in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbff52ab0 "ASSERT: \"service\" in file /home/mandrake/rpm/BUILD/kdebase-4.1.2/apps/konqueror/settings/filetypes/kservicelistwidget.cpp, line 247")
    at global/qglobal.cpp:2102
#10 0x4e083bd5 in qFatal (msg=<value optimized out>) at global/qglobal.cpp:2303
#11 0x4e083c85 in qt_assert (assertion=) at global/qglobal.cpp:1872
#12 0xb66dab60 in KServiceListWidget::addService (this=0x9e22a98)
    at /usr/src/debug/kdebase-4.1.2/apps/konqueror/settings/filetypes/kservicelistwidget.cpp:247
#13 0xb66dc158 in KServiceListWidget::qt_metacall (this=0x9e22a98, 
    _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0xbff54c90)
    at /usr/src/debug/kdebase-4.1.2/build/apps/konqueror/settings/filetypes/kservicelistwidget.moc:79
#14 0x4e19a32d in QMetaObject::activate (sender=) at kernel/qobject.cpp:3031
#15 0x4e19a75b in QMetaObject::activate (sender=<value optimized out>, m=)
    at kernel/qobject.cpp:3121
#16 0x42ff1a95 in QAbstractButton::clicked (this=)
    at .moc/release-shared/moc_qabstractbutton.cpp:185
#17 0x42d2e68d in QAbstractButtonPrivate::emitClicked (
    this=<value optimized out>) at widgets/qabstractbutton.cpp:538
#18 0x42d3034b in QAbstractButtonPrivate::click (this=<value optimized out>)
    at widgets/qabstractbutton.cpp:531
#19 0x42d305e6 in QAbstractButton::mouseReleaseEvent (
    this=<value optimized out>, e=<value optimized out>)
    at widgets/qabstractbutton.cpp:1110
#20 0x42a2c04a in QWidget::event (this=0x9effd98, event=0xbff55248)
    at kernel/qwidget.cpp:7163
#21 0x42d2e510 in QAbstractButton::event (this=<value optimized out>, 
    e=<value optimized out>) at widgets/qabstractbutton.cpp:1072
#22 0x42dd9633 in QPushButton::event (this=<value optimized out>, 
    e=<value optimized out>) at widgets/qpushbutton.cpp:652
#23 0x429d162c in QApplicationPrivate::notify_helper (
    this=<value optimized out>, receiver=<value optimized out>, 
    e=<value optimized out>) at kernel/qapplication.cpp:3803
#24 0x429da26f in QApplication::notify (this=0xbff55ac4, receiver=0x9effd98, 
    e=0xbff55248) at kernel/qapplication.cpp:3528
#25 0x433976b1 in KApplication::notify (this=<value optimized out>, receiver=)
    at /usr/src/debug/kdelibs-4.1.2/kdeui/kernel/kapplication.cpp:311
#26 0x4e184ef3 in QCoreApplication::notifyInternal (this=)
    at kernel/qcoreapplication.cpp:587
#27 0x429d9491 in QApplicationPrivate::sendMouseEvent (
    receiver=<value optimized out>, event=)
    at ../../src/corelib/kernel/qcoreapplication.h:212
#28 0x42a4639d in QETWidget::translateMouseEvent (this=<value optimized out>, 
    event=<value optimized out>) at kernel/qapplication_x11.cpp:4042
#29 0x42a45800 in QApplication::x11ProcessEvent (this=0xbff55ac4, 
    event=0xbff557fc) at kernel/qapplication_x11.cpp:3038
#30 0x42a6e884 in x11EventSourceDispatch (s=<value optimized out>, 
    callback=<value optimized out>, user_data=<value optimized out>)
    at kernel/qguieventdispatcher_glib.cpp:142
#31 0x4ef237ca in IA__g_main_context_dispatch (context=) at gmain.c:2142
#32 0x4ef26ee8 in g_main_context_iterate (context=<value optimized out>, 
    block=<value optimized out>, dispatch=) at gmain.c:2776
#33 0x4ef270a8 in IA__g_main_context_iteration (context=<value optimized out>, 
    may_block=) at gmain.c:2839
#34 0x4e1b09ea in QEventDispatcherGlib::processEvents (this=)
    at kernel/qeventdispatcher_glib.cpp:319
#35 0x42a6dfda in QGuiEventDispatcherGlib::processEvents (this=)
    at kernel/qguieventdispatcher_glib.cpp:198
#36 0x4e183563 in QEventLoop::processEvents (this=)
    at kernel/qeventloop.cpp:143
#37 0x4e183721 in QEventLoop::exec (this=<value optimized out>, flags=)
    at kernel/qeventloop.cpp:194
#38 0x4e185e92 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:845
#39 0x429d1494 in QApplication::exec () at kernel/qapplication.cpp:3331
#40 0x08055d0b in _start ()

Mandriva has released updates from kde 4.1.2 to kde 4.1.3, which fixes this bug.