Version:            (using KDE 4.2.96)
OS:                Linux
Installed from:    Ubuntu Packages

I restarted DBus and the services that depend on it (NetworkManager, etc.), and that caused KBluetooth4 to crash:

Application: KBluetooth4 - The KDE4 Bluetooth Framework (kbluetooth4), signal: Segmentation fault
[KCrash Handler]
#5  0x00007f56b563a935 in QObject::property (this=0x1a74c60, name=0x7f56b597b580 "_qdbus_slotCache") at kernel/qobject.cpp:3300
#6  0x00007f56b59432fe in QDBusConnectionPrivate::activateCall (this=0x19dbca0, object=0x1a74c60, flags=273, msg=@0x19fb6f0) at qdbusintegrator.cpp:753
#7  0x00007f56b5943d81 in QDBusConnectionPrivate::activateObject (this=0x19dbca0, node=@0x19fb6c8, msg=@0x19fb6f0, pathStartPos=<value optimized out>) at qdbusintegrator.cpp:1352
#8  0x00007f56b5944098 in QDBusActivateObjectEvent::placeMetaCall (this=0x19fb680) at qdbusintegrator.cpp:1469
#9  0x00007f56b5637f28 in QObject::event (this=0x7fffbfc057b0, e=0x19fb680) at kernel/qobject.cpp:1118
#10 0x00007f56b4a8131a in QApplication::event (this=0x7fffbfc057b0, e=0x19fb680) at kernel/qapplication.cpp:2318
#11 0x00007f56b4a7bb9d in QApplicationPrivate::notify_helper (this=0x19223b0, receiver=0x7fffbfc057b0, e=0x19fb680) at kernel/qapplication.cpp:4057
#12 0x00007f56b4a83dea in QApplication::notify (this=0x7fffbfc057b0, receiver=0x7fffbfc057b0, e=0x19fb680) at kernel/qapplication.cpp:4022
#13 0x00007f56b713463b in KApplication::notify (this=0x7fffbfc057b0, receiver=0x7fffbfc057b0, event=0x19fb680) at /build/buildd/kde4libs-4.2.96/kdeui/kernel/kapplication.cpp:302
#14 0x00007f56b5627dfc in QCoreApplication::notifyInternal (this=0x7fffbfc057b0, receiver=0x7fffbfc057b0, event=0x19fb680) at kernel/qcoreapplication.cpp:610
#15 0x00007f56b5628a6a in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x18fb320) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#16 0x00007f56b56518a3 in postEventSourceDispatch (s=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#17 0x00007f56b087d20a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#18 0x00007f56b08808e0 in ?? () from /usr/lib/libglib-2.0.so.0
#19 0x00007f56b0880a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#20 0x00007f56b565152f in QEventDispatcherGlib::processEvents (this=0x18fab50, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:324
#21 0x00007f56b4b1470f in QGuiEventDispatcherGlib::processEvents (this=0x1a74c60, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#22 0x00007f56b56266a2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = -1077919936}) at kernel/qeventloop.cpp:149
#23 0x00007f56b5626a6d in QEventLoop::exec (this=0x7fffbfc04040, flags={i = -1077919312}) at kernel/qeventloop.cpp:200
#24 0x00007f56b5947226 in QDBusConnectionPrivate::sendWithReply (this=0x1a9bae0, message=@0x7fffbfc04370, sendMode=<value optimized out>, timeout=-1) at qdbusintegrator.cpp:1787
#25 0x00007f56b5930aa3 in QDBusConnection::call (this=0x1a6b440, message=@0x7f56b597b580, mode=27244272, timeout=4362581) at qdbusconnection.cpp:516
#26 0x00007f56b594e6df in QDBusAbstractInterface::callWithArgumentList (this=0x1aa2150, mode=QDBus::BlockWithGui, method=<value optimized out>, args=@0x7fffbfc04470) at qdbusabstractinterface.cpp:402
#27 0x00007f56b59523ac in QDBusAbstractInterface::call (this=0x1aa2150, mode=QDBus::BlockWithGui, method=@0x7fffbfc045a0, arg1=@0x7fffbfc04560, arg2=@0x7fffbfc04550, arg3=@0x7fffbfc04540, 
    arg4=@0x7fffbfc04530, arg5=@0x7fffbfc04520, arg6=@0x7fffbfc04510, arg7=@0x7fffbfc04500, arg8=@0x7fffbfc044f0) at qdbusabstractinterface.cpp:655
#28 0x0000000000420e2e in _start ()