I now have enough debugging symbols on my machine to have a more informative stacktrace from a plasma crash characteristic of this bug. In this case, the display had been drawing badly for some time as characterized by the already included screenshots. Then this crash happened:

Application: Plasma Workspace (plasma), signal SIGSEGV
0x00007f83e965ad21 in nanosleep () from /lib/libc.so.6
Current language:  auto; currently c
[Current thread is 0 (LWP 4698)]

Thread 5 (Thread 0x7f83cecc7950 (LWP 4701)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f83ea13c939 in QWaitCondition::wait (this=0x29a6d80, mutex=0x29a6d78, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f83ed8f84cc in QHostInfoAgent::run (this=0x29a6d60) at kernel/qhostinfo.cpp:260
#3  0x00007f83ea13b952 in QThreadPrivate::start (arg=0x29a6d60) at thread/qthread_unix.cpp:189
#4  0x00007f83e6a903ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#5  0x00007f83e9698fcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()

Thread 4 (Thread 0x7f83cd85c950 (LWP 4702)):
#0  0x00007f83e9691742 in select () from /lib/libc.so.6
#1  0x00007f83ea202f06 in QProcessManager::run (this=0x2257720) at io/qprocess_unix.cpp:305
#2  0x00007f83ea13b952 in QThreadPrivate::start (arg=0x2257720) at thread/qthread_unix.cpp:189
#3  0x00007f83e6a903ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#4  0x00007f83e9698fcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#5  0x0000000000000000 in ?? ()
Current language:  auto; currently asm

Thread 3 (Thread 0x7f83ccc3d950 (LWP 4704)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f83ea13c939 in QWaitCondition::wait (this=0x26c65e0, mutex=0x26c65d8, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f83d020fd4e in RenderThread::run (this=0x26c65c8) at /build/buildd/kdebase-workspace-4.2.2/plasma/wallpapers/image/renderthread.cpp:91
#3  0x00007f83ea13b952 in QThreadPrivate::start (arg=0x26c65c8) at thread/qthread_unix.cpp:189
#4  0x00007f83e6a903ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#5  0x00007f83e9698fcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()
Current language:  auto; currently c

Thread 2 (Thread 0x7f83de3c2950 (LWP 4918)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
#1  0x00007f83ea13c939 in QWaitCondition::wait (this=0x265a350, mutex=0x265a348, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:87
#2  0x00007f83d020fd4e in RenderThread::run (this=0x265a338) at /build/buildd/kdebase-workspace-4.2.2/plasma/wallpapers/image/renderthread.cpp:91
#3  0x00007f83ea13b952 in QThreadPrivate::start (arg=0x265a338) at thread/qthread_unix.cpp:189
#4  0x00007f83e6a903ba in start_thread (arg=<value optimized out>) at pthread_create.c:297
#5  0x00007f83e9698fcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#6  0x0000000000000000 in ?? ()
Current language:  auto; currently asm

Thread 1 (Thread 0x7f83eedaa760 (LWP 4698)):
[KCrash Handler]
#5  0x0000000000000000 in ?? ()
#6  0x00007f83eab111c4 in blend_src_generic<RegularSpans> (count=131, spans=0x32a31f8, userData=<value optimized out>) at painting/qdrawhelper.cpp:3389
#7  0x00007f83eab12e9e in blend_transformed_bilinear_tiled_argb<RegularSpans> (count=-153236880, spans=0x7ffff6de0a70, userData=0x398ed10) at painting/qdrawhelper.cpp:5741
#8  0x00007f83eab46d87 in gray_convert_glyph (worker=0x32a2a80) at painting/qgrayraster.c:1771
#9  0x00007f83eaaeae99 in QRasterPaintEnginePrivate::rasterize (this=0x2d4a2d0, outline=0x3373ef0, callback=0x7f83eab030e0 <qBlendTexture(int, QT_FT_Span_ const*, void*)>, 
    userData=<value optimized out>) at painting/qpaintengine_raster.cpp:3948
#10 0x00007f83eaaf2f2b in QRasterPaintEngine::fillPath (this=0x32f68b0, path=@0x7ffff6de3690, fillData=0x398ed10) at painting/qpaintengine_raster.cpp:1364
#11 0x00007f83eaafdd01 in QRasterPaintEngine::drawPath (this=0x32f68b0, path=@0x7ffff6de3690) at painting/qpaintengine_raster.cpp:1887
#12 0x00007f83eaa89b8d in QPainterPrivate::draw_helper (this=0x36293c0, originalPath=@0x7ffff6de3690, op=<value optimized out>) at painting/qpainter.cpp:451
#13 0x00007f83eaa8cb27 in QPainter::drawRects (this=<value optimized out>, rects=<value optimized out>, rectCount=1) at painting/qpainter.cpp:3359
#14 0x00007f83eaa8ec7e in QPainter::drawPixmap (this=0x7ffff6de4de0, r=<value optimized out>, pm=@0x7ffff6de3890, sr=<value optimized out>)
    at ../../include/QtGui/../../src/gui/painting/qpainter.h:604
#15 0x00007f83ee65b73f in Plasma::Svg::paint () from /usr/lib/libplasma.so.3
#16 0x00007f83ee67b994 in ?? () from /usr/lib/libplasma.so.3
#17 0x00007f83ee67b84a in Plasma::Meter::paint () from /usr/lib/libplasma.so.3
#18 0x00007f83eaf50ff5 in _q_paintItem (item=<value optimized out>, painter=0x7ffff6de4de0, option=0x2fde730, widget=0x2fefcc0, useWindowOpacity=true, painterStateProtection=true)
    at graphicsview/qgraphicsscene.cpp:4483
#19 0x00007f83eaf526e8 in QGraphicsScenePrivate::drawItemHelper (this=<value optimized out>, item=0x2adbed0, painter=0x7ffff6de4de0, option=0x2fde730, widget=0x2fefcc0, painterStateProtection=true)
    at graphicsview/qgraphicsscene.cpp:4552
#20 0x00007f83eaf547fe in QGraphicsScene::drawItems (this=<value optimized out>, painter=0x7ffff6de4de0, numItems=41, items=<value optimized out>, options=0x2fdde30, widget=0x2fefcc0)
    at graphicsview/qgraphicsscene.cpp:4957
#21 0x00007f83eaf76540 in QGraphicsView::paintEvent (this=0x28eb600, event=<value optimized out>) at graphicsview/qgraphicsview.cpp:3542
#22 0x00007f83ea9ba796 in QWidget::event (this=0x28eb600, event=0x7ffff6de5590) at kernel/qwidget.cpp:7654
#23 0x00007f83ead546eb in QFrame::event (this=0x28eb600, e=0x7ffff6de5590) at widgets/qframe.cpp:559
#24 0x00007f83eaf70ffb in QGraphicsView::viewportEvent (this=0x28eb600, event=0x7ffff6de5590) at graphicsview/qgraphicsview.cpp:2933
#25 0x00007f83ea223a68 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<value optimized out>, receiver=0x2fefcc0, event=0x7ffff6de5590) at kernel/qcoreapplication.cpp:718
#26 0x00007f83ea96980c in QApplicationPrivate::notify_helper (this=0x2263aa0, receiver=0x2fefcc0, e=0x7ffff6de5590) at kernel/qapplication.cpp:4080
#27 0x00007f83ea971a2a in QApplication::notify (this=0x225a010, receiver=0x2fefcc0, e=0x7ffff6de5590) at kernel/qapplication.cpp:4049
#28 0x00007f83ed02626b in KApplication::notify (this=0x225a010, receiver=0x2fefcc0, event=0x7ffff6de5590) at /build/buildd/kde4libs-4.2.2/kdeui/kernel/kapplication.cpp:307
#29 0x00007f83ea22475c in QCoreApplication::notifyInternal (this=0x225a010, receiver=0x2fefcc0, event=0x7ffff6de5590) at kernel/qcoreapplication.cpp:602
#30 0x00007f83ea9c1a55 in QWidgetPrivate::drawWidget (this=0x2fefcf0, pdev=0x26cf328, rgn=@0x7ffff6de5900, offset=@0x7ffff6de58f0, flags=68, sharedPainter=0x0, backingStore=0x2fa6280)
    at kernel/qwidget.cpp:5046
#31 0x00007f83eab653ae in QWidgetBackingStore::sync (this=0x2fa6280) at painting/qbackingstore.cpp:1258
#32 0x00007f83ea9b3100 in QWidgetPrivate::syncBackingStore (this=0x28765f0) at kernel/qwidget.cpp:1603
#33 0x00007f83ea9ba62d in QWidget::event (this=0x28eb600, event=0x288f820) at kernel/qwidget.cpp:7794
#34 0x00007f83ead546eb in QFrame::event (this=0x28eb600, e=0x288f820) at widgets/qframe.cpp:559
#35 0x00007f83eade5c29 in QAbstractScrollArea::event (this=0x28eb600, e=0x288f820) at widgets/qabstractscrollarea.cpp:918
#36 0x00007f83ea96983d in QApplicationPrivate::notify_helper (this=0x2263aa0, receiver=0x28eb600, e=0x288f820) at kernel/qapplication.cpp:4084
#37 0x00007f83ea971a2a in QApplication::notify (this=0x225a010, receiver=0x28eb600, e=0x288f820) at kernel/qapplication.cpp:4049
#38 0x00007f83ed02626b in KApplication::notify (this=0x225a010, receiver=0x28eb600, event=0x288f820) at /build/buildd/kde4libs-4.2.2/kdeui/kernel/kapplication.cpp:307
#39 0x00007f83ea22475c in QCoreApplication::notifyInternal (this=0x225a010, receiver=0x28eb600, event=0x288f820) at kernel/qcoreapplication.cpp:602
#40 0x00007f83ea2253ca in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x2217a30) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#41 0x00007f83ea24e1e3 in postEventSourceDispatch (s=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#42 0x00007f83e4e6020a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#43 0x00007f83e4e638e0 in ?? () from /usr/lib/libglib-2.0.so.0
#44 0x00007f83e4e63a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#45 0x00007f83ea24de6f in QEventDispatcherGlib::processEvents (this=0x221bea0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:323
#46 0x00007f83eaa01c9f in QGuiEventDispatcherGlib::processEvents (this=0x7ffff6ddca70, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#47 0x00007f83ea223002 in QEventLoop::processEvents (this=<value optimized out>, flags={i = -153197488}) at kernel/qeventloop.cpp:149
#48 0x00007f83ea2233cd in QEventLoop::exec (this=0x7ffff6de6490, flags={i = -153197408}) at kernel/qeventloop.cpp:200
#49 0x00007f83ea225694 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#50 0x00007f83ee9859bb in kdemain (argc=1, argv=0x7ffff6de6798) at /build/buildd/kdebase-workspace-4.2.2/plasma/shells/desktop/main.cpp:54
#51 0x00007f83e95d15a6 in __libc_start_main (main=0x400890 <main>, argc=1, ubp_av=0x7ffff6de6798, init=0x4008c0 <__libc_csu_init>, fini=<value optimized out>, rtld_fini=<value optimized out>, 
    stack_end=0x7ffff6de6788) at libc-start.c:220
#52 0x00000000004007c9 in _start () at ../sysdeps/x86_64/elf/start.S:113
#0  0x00007f83e965ad21 in nanosleep () from /lib/libc.so.6
Current language:  auto; currently c