After the latest Debian sid update, Digikam quit working on one of my machines (but not the other). It would flash the start-up logo, then just disappear. Googling for this didn't turn up an answer, so I tried launching digikam from the command line, which gave me some error messages to search with. I found this discussion in a forum:
For some reason Dolphin (version 1.7) and digikam (version 1.9.0) keep crashing on me. Dolphin will crash on me every time my mouse cursor is over a video file. When I start digikam it will start to load and than disappear. I have just updated to kde 4.7.4 on AMD64 but this issue was happening before the upgrade. I have tried to run both programs from the console and I receive the same error message.
[0x16865a0] main services discovery error: no suitable services discovery module digikam: symbol lookup error: /usr/lib/qt4/plugins/phonon_backend/phonon_vlc.so: undefined symbol: libvlc_audio_filter_list_get
That's exactly the sort of problem I was having (I don't use Dolphin very often, so I hadn't noticed that issue). Why sound module problems would affect a photo management problem is not obvious to me, but eventually the original poster announced:
I have solved the issue. I removed vlc-data along with it's dependencies which included phonon-backend-vlc. Now dolphin, digikam and system-settings do not crash for me. Now the only backend I have installed is gstreamer. I guess there is just something wrong with the phonon-backend-vlc package.
I immediately added the replacement for phonon-backend-vlc:
aptitude install phonon-backend-gstreamer
And the problem was solved. (I didn't bother to remove phonon-backend-vlc; it seems that phonon-backend-gstreamer just replaced it (and the forum participants indicated that there were problems involved in removing phonon-backend-vlc).