The same. Terminal output is:

~ $ digikam
Object::connect: No such signal org::freedesktop::UPower::DeviceAdded(QString)
Object::connect: No such signal org::freedesktop::UPower::DeviceRemoved(QString)
QSqlDatabasePrivate::removeDatabase: connection 'ConnectionTest' is still in use, all queries will cease to work.

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstBaseAudioSink' is smaller than the parent type's 'GstBaseSink' class size

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_register_static: assertion 'parent_type > 0' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstAlsaSrc' is smaller than the parent type's 'GstAudioSrc' class size

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstCapsFilter' is smaller than the parent type's 'GstBaseTransform' class size

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed

(digikam:7536): GStreamer-CRITICAL **: gst_bin_add: assertion 'GST_IS_ELEMENT (element)' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_get_static_pad: assertion 'GST_IS_ELEMENT (element)' failed

(digikam:7536): GStreamer-CRITICAL **: gst_object_unref: assertion 'object != NULL' failed

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstBaseAudioSrc' is smaller than the parent type's 'GstPushSrc' class size

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_register_static: assertion 'parent_type > 0' failed

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstOss4Sink' is smaller than the parent type's 'GstAudioSink' class size

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed

(digikam:7536): GLib-GObject-WARNING **: specified class size for type 'GstOssSrc' is smaller than the parent type's 'GstAudioSrc' class size

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-GObject-CRITICAL **: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed

(digikam:7536): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(digikam:7536): GStreamer-CRITICAL **: gst_element_register: assertion 'g_type_is_a (type, GST_TYPE_ELEMENT)' failed
KCrash: Application 'digikam' crashing...
KCrash: Attempting to start /usr/lib/kde4/libexec/drkonqi from kdeinit
sock_file=/home/user/.kde4/socket-host/kdeinit4__0

[1]+ Stopped digikam
~ $ QSocketNotifier: Invalid socket 20 and type 'Read', disabling...

[1]+ Exit 253 digikam
~ $

Same here on my machine, fully updated x86_64.

Quick workaround is to uninstall gstreamer0.10-good-plugins and gstreamer0.10-good, but than other applications don't work, so this is not a solution for a longer time.

What does pacman want to delete with pacman -Rc gstreamer0.10?
Looks like mixed gstreamer versions in one process.

~ $ sudo pacman -Rc gstreamer0.10
checking dependencies...
:: kipi-plugins optionally requires opencv: Remove Red Eyes plugin
:: libnice optionally requires gstreamer0.10
:: libqalculate optionally requires gnuplot: for plotting support
:: openbabel optionally requires wxgtk2.8: GUI interface
:: opera optionally requires gstreamer0.10-base-plugins: HTML5 Video support
:: opera optionally requires gstreamer0.10-good: HTML5 Video support
:: p7zip optionally requires wxgtk2.8: GUI
:: python2-pyqt5 optionally requires qt5-multimedia: QtMultimedia, QtMultimediaWidgets
:: sysstat optionally requires gnuplot: to use isag
:: telepathy-kde-accounts-kcm optionally requires telepathy-haze: all protocols supported by libpurple

Packages (33): audacity-2.0.5-2 cantata-1.4.1-1 clementine-1.2.3-2 digikam-4.2.0-2 farstream-0.1-0.1.2-4 filezilla-3.9.0.5-1 frei0r-plugins-1.4-2 gnuplot-4.6.5-1 gstreamer0.10-bad-0.10.23-8 gstreamer0.10-bad-plugins-0.10.23-8
gstreamer0.10-base-0.10.36-3 gstreamer0.10-base-plugins-0.10.36-3 gstreamer0.10-ffmpeg-0.10.13-2 gstreamer0.10-good-0.10.31-6 gstreamer0.10-good-plugins-0.10.31-6 gstreamer0.10-python-0.10.22-2
gstreamer0.10-ugly-0.10.19-12 gstreamer0.10-ugly-plugins-0.10.19-12 kdenlive-0.9.8-2 libkface-4.2.0-2 libpurple-2.10.9-2 mlt-0.9.2-1 myrulib-0.29.16-2 opencv-2.4.9-3 pgadmin3-1.18.1-8 pidgin-2.10.9-2
purple-plugin-pack-2.7.0-2 qt5-multimedia-5.3.1-1 telepathy-haze-0.8.0-1 telepathy-kde-call-ui-0.8.1-1 wxgtk-3.0.1-3 wxgtk2.8-2.8.12.1-2 gstreamer0.10-0.10.36-4

Total Removed Size: 379.71 MiB

:: Do you want to remove these packages? [Y/n] ^C
Interrupt signal received

~ $

Guess it's linked in trough opencv and kipi plugins.

~ $ pactree -r gstreamer0.10
gstreamer0.10
└─gstreamer0.10-base
├─clementine
├─farstream-0.1
│ ├─libpurple
│ │ ├─pidgin
│ │ ├─purple-plugin-pack
│ │ └─telepathy-haze
│ └─telepathy-kde-call-ui
├─gstreamer0.10-bad
│ └─gstreamer0.10-bad-plugins
│ └─farstream-0.1
├─gstreamer0.10-base-plugins
├─gstreamer0.10-ffmpeg
│ └─farstream-0.1
├─gstreamer0.10-good
│ └─gstreamer0.10-good-plugins
│ └─farstream-0.1
├─gstreamer0.10-python
├─gstreamer0.10-ugly
│ └─gstreamer0.10-ugly-plugins
├─opencv
│ ├─digikam
│ ├─frei0r-plugins
│ │ └─mlt
│ │ └─kdenlive
│ └─libkface
│ └─digikam
├─qt5-multimedia
│ └─cantata
├─wxgtk
│ └─filezilla
└─wxgtk2.8
├─audacity
├─gnuplot
├─myrulib
└─pgadmin3

gstreamer0.10
└─gstreamer0.10-base
├─gstreamer0.10-bad
│ └─gstreamer0.10-bad-plugins
├─gstreamer0.10-base-plugins
│ └─xfce4-mixer
├─gstreamer0.10-ffmpeg
├─gstreamer0.10-good
├─gstreamer0.10-ugly
│ └─gstreamer0.10-ugly-plugins
├─opencv
│ ├─digikam
│ └─libkface
│ └─digikam
├─wxgtk
│ ├─filezilla
│ └─hugin
└─wxgtk2.8
├─audacity
└─truecrypt

The problem seems to be related with opencv.

The problem persists also with digikam 4.3

Please try opencv 2.4.9-4.

I disabled GStreamer support in that package, as opencv doesn't support GStreamer 1.0 at this moment. Upstream has 1.0 support in the master branch which we could backport (Fedora has it in Rawhide), but so far they haven't enabled it.

Now it works.
But I've also reinstalled gstreamer0.10. The problem was probably related with a gs-plugin.

No, the problem was that digicam depends on gstreamer 1.0 through phonon and qtwebkit, while opencv links to gstreamer0.10. This is a totally unsupported configuration which is known to fail.