Application: digikam (2.8.0)
KDE Platform Version: 4.8.4 (4.8.4)
Qt Version: 4.8.1
Operating System: Linux 3.2.0-27-generic x86_64
Distribution: Linux Mint 13 Maya

-- Information about the crash:
Go to Tools → Maintenance → and check [✔] Rebuild Thumbnails.  Click [OK].  Most times Digikam freezes, but this last time it crashed (I guess that's good).

Before it crashes, the thumbnails aren't visible.  The thumbnail file format is Nikon's NEF raw image format, though other file formats don's show up, either.

When clicking on an image, the image shows up just fine in the preview.

THIS MIGHT BE A RELATED BUG:

Right click on an image preview and go into Edit mode.  Edit the image.  Go to File → Save As New Version → PNG.  The edit window will hang indefinitely after saving 100%.  After killing the application and restarting, I find that the new version of the image was saved.

-- Backtrace:
Application: digiKam (digikam), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f518d504840 (LWP 5264))]

Thread 4 (Thread 0x7f5160aca700 (LWP 5303)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
#1  0x00007f518796d4db in wait (time=18446744073709551615, this=0x2792cd0) at thread/qwaitcondition_unix.cpp:86
#2  QWaitCondition::wait (this=<optimized out>, mutex=0x2792bc8, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:158
#3  0x00000000005d6a30 in Digikam::ScanController::run (this=0x2792960) at /build/buildd/digikam-2.8.0/core/digikam/database/scancontroller.cpp:698
#4  0x00007f518796cfcb in QThreadPrivate::start (arg=0x2792960) at thread/qthread_unix.cpp:298
#5  0x00007f517d49a6d4 in ?? () from /usr/lib/libGL.so.1
#6  0x00007f5182353e9a in start_thread (arg=0x7f5160aca700) at pthread_create.c:308
#7  0x00007f5186b994bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#8  0x0000000000000000 in ?? ()

Thread 3 (Thread 0x7f515bfff700 (LWP 5305)):
#0  0x00007f5186b8db03 in __GI___poll (fds=<optimized out>, nfds=<optimized out>, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:87
#1  0x00007f517ffa3036 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007f517ffa3164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f5187a9b426 in QEventDispatcherGlib::processEvents (this=0x7f51540008f0, flags=...) at kernel/qeventdispatcher_glib.cpp:426
#4  0x00007f5187a6ac82 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#5  0x00007f5187a6aed7 in QEventLoop::exec (this=0x7f515bffec50, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f5187969fa7 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:501
#7  0x00007f5187a4a9ff in QInotifyFileSystemWatcherEngine::run (this=0x27960d0) at io/qfilesystemwatcher_inotify.cpp:248
#8  0x00007f518796cfcb in QThreadPrivate::start (arg=0x27960d0) at thread/qthread_unix.cpp:298
#9  0x00007f517d49a6d4 in ?? () from /usr/lib/libGL.so.1
#10 0x00007f5182353e9a in start_thread (arg=0x7f515bfff700) at pthread_create.c:308
#11 0x00007f5186b994bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#12 0x0000000000000000 in ?? ()

Thread 2 (Thread 0x7f515ae12700 (LWP 5609)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
#1  0x00007f518796d4db in wait (time=18446744073709551615, this=0x2ad6410) at thread/qwaitcondition_unix.cpp:86
#2  QWaitCondition::wait (this=<optimized out>, mutex=0x27db108, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:158
#3  0x00007f518ad8ea11 in Digikam::ParkingThread::run (this=0x27db0f0) at /build/buildd/digikam-2.8.0/core/libs/threads/threadmanager.cpp:119
#4  0x00007f518796cfcb in QThreadPrivate::start (arg=0x27db0f0) at thread/qthread_unix.cpp:298
#5  0x00007f517d49a6d4 in ?? () from /usr/lib/libGL.so.1
#6  0x00007f5182353e9a in start_thread (arg=0x7f515ae12700) at pthread_create.c:308
#7  0x00007f5186b994bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#8  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f518d504840 (LWP 5264)):
[KCrash Handler]
#6  QMutex::lock (this=0x50) at thread/qmutex.cpp:150
#7  0x00007f518ad3d5b4 in Digikam::ThumbnailDatabaseAccess::ThumbnailDatabaseAccess (this=<optimized out>) at /build/buildd/digikam-2.8.0/core/libs/database/core/thumbnaildatabaseaccess.cpp:87
#8  0x000000000051a5cf in Digikam::ThumbsGenerator::slotStart (this=0x6e2f280) at /build/buildd/digikam-2.8.0/core/utilities/maintenance/thumbsgenerator.cpp:130
#9  0x0000000000520415 in Digikam::MaintenanceMngr::slotStage1 (this=0x6e406c0) at /build/buildd/digikam-2.8.0/core/utilities/maintenance/maintenancemngr.cpp:118
#10 0x0000000000520746 in Digikam::MaintenanceMngr::setSettings (this=0x6e406c0, settings=...) at /build/buildd/digikam-2.8.0/core/utilities/maintenance/maintenancemngr.cpp:98
#11 0x000000000058150b in Digikam::DigikamApp::slotMaintenance (this=0x27e8710) at /build/buildd/digikam-2.8.0/core/digikam/main/digikamapp.cpp:2582
#12 0x000000000058cdda in Digikam::DigikamApp::qt_static_metacall (_o=0x27e8710, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at /build/buildd/digikam-2.8.0/obj-x86_64-linux-gnu/core/digikam/digikamapp.moc:204
#13 0x00007f5187a80281 in QMetaObject::activate (sender=0x3a20450, m=<optimized out>, local_signal_index=<optimized out>, argv=0x7fff5a2ddef0) at kernel/qobject.cpp:3547
#14 0x00007f5188460132 in QAction::triggered (this=<optimized out>, _t1=false) at .moc/release-shared/moc_qaction.cpp:277
#15 0x00007f518846031f in QAction::activate (this=0x3a20450, event=<optimized out>) at kernel/qaction.cpp:1257
#16 0x00007f51888b2119 in QMenuPrivate::activateCausedStack (this=0x3b47290, causedStack=..., action=0x3a20450, action_e=QAction::Trigger, self=true) at widgets/qmenu.cpp:1028
#17 0x00007f51888b8272 in QMenuPrivate::activateAction (this=0x3b47290, action=0x3a20450, action_e=QAction::Trigger, self=true) at widgets/qmenu.cpp:1120
#18 0x00007f51892612d0 in KMenu::mouseReleaseEvent (this=0x2c98840, e=0x7fff5a2deac0) at ../../kdeui/widgets/kmenu.cpp:464
#19 0x00007f51884b7144 in QWidget::event (this=0x2c98840, event=0x7fff5a2deac0) at kernel/qwidget.cpp:8362
#20 0x00007f51888b980b in QMenu::event (this=0x2c98840, e=0x7fff5a2deac0) at widgets/qmenu.cpp:2469
#21 0x00007f5188466894 in notify_helper (e=0x7fff5a2deac0, receiver=0x2c98840, this=0x24bdbd0) at kernel/qapplication.cpp:4559
#22 QApplicationPrivate::notify_helper (this=0x24bdbd0, receiver=0x2c98840, e=0x7fff5a2deac0) at kernel/qapplication.cpp:4531
#23 0x00007f518846c0bf in QApplication::notify (this=<optimized out>, receiver=0x2c98840, e=0x7fff5a2deac0) at kernel/qapplication.cpp:4102
#24 0x00007f51891a09e6 in KApplication::notify (this=0x7fff5a2df8b0, receiver=0x2c98840, event=0x7fff5a2deac0) at ../../kdeui/kernel/kapplication.cpp:311
#25 0x00007f5187a6be9c in QCoreApplication::notifyInternal (this=0x7fff5a2df8b0, receiver=0x2c98840, event=0x7fff5a2deac0) at kernel/qcoreapplication.cpp:876
#26 0x00007f5188467862 in sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#27 QApplicationPrivate::sendMouseEvent (receiver=0x2c98840, event=0x7fff5a2deac0, alienWidget=0x0, nativeWidget=0x2c98840, buttonDown=0x0, lastMouseReceiver=..., spontaneous=true) at kernel/qapplication.cpp:3170
#28 0x00007f51884e72c1 in QETWidget::translateMouseEvent (this=0x2c98840, event=<optimized out>) at kernel/qapplication_x11.cpp:4551
#29 0x00007f51884e5bae in QApplication::x11ProcessEvent (this=0x7fff5a2df8b0, event=0x7fff5a2df390) at kernel/qapplication_x11.cpp:3732
#30 0x00007f518850f0d2 in x11EventSourceDispatch (s=0x24be570, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#31 0x00007f517ffa2d53 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#32 0x00007f517ffa30a0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33 0x00007f517ffa3164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#34 0x00007f5187a9b3bf in QEventDispatcherGlib::processEvents (this=0x2455de0, flags=...) at kernel/qeventdispatcher_glib.cpp:424
#35 0x00007f518850ed5e in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#36 0x00007f5187a6ac82 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#37 0x00007f5187a6aed7 in QEventLoop::exec (this=0x7fff5a2df730, flags=...) at kernel/qeventloop.cpp:204
#38 0x00007f5187a6ff67 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1148
#39 0x000000000048f63b in main (argc=5, argv=<optimized out>) at /build/buildd/digikam-2.8.0/core/digikam/main/main.cpp:232

Reported using DrKonqi