Version:           0.7 (using KDE KDE 3.4.3)
Installed from:    Ubuntu Packages
OS:                Linux

I opened the following bug at the Ubuntu bugzilla:

After changing the playback engine from GStreamer to Xine, Kaffeine doesn't work properly until it is restarted. Most notably, it is unable to play DVDs (xine-engine complains about not supporting DVD navigation) - a restart fixes it. I suspect there are other such issues, so I suggest that Kaffeine should force a restart after the playback engine is changed.

http://bugzilla.ubuntu.com/show_bug.cgi?id=18195

To expand on that, the full console output when trying to play a DVD having just switched from GStreamer to Xine (without a restart) is:
libdvdnav: Using dvdnav version 0.1.9 from http://dvd.sf.net
libdvdread: Using libdvdcss version 1.2.8 for DVD access
libdvdnav: DVD Title: RICKY_GERVAIS_POLITICS
libdvdnav: DVD Serial Number: 31377764
libdvdnav: DVD Title (Alternative): RICKY_GERVAIS_POLITICS
libdvdnav: Unable to find map file '/home/dj/.dvdnav/RICKY_GERVAIS_POLITICS.map'
libdvdread: Can't open file VIDEO_TS.IFO.
libdvdnav: vm: faild to read VIDEO_TS.IFO

Kaffeine gives a 'No plugin found to handle this resource (dvd:/)' message with the following errors shown in 'details':
xine: cannot find input plugin for MRL [dvd:/]
xine: input plugin cannot open MRL [dvd:/]
xine: found input plugin : DVD Navigator