OK, so it seems the problem lies in my local cache having a priority of 9999, whereas yours is only 500.
I look in /etc/apt/preferences, and find:
Pin: release v=8.10,o=Ubuntu,a=hardy,l=Ubuntu
I assume yours is different? Why does mine look like that?
Also, my core has the following preferences:
# We take MythTV from our repo always
Package: mythtv mythtv-frontend mythtv-backend mythtv-common mythtv-database mythtv-transcode-utils mythweb libmythtv-perl libmyth python-myth mythtv-themes mythplugins mytharchive mytharchive-data mythbrowser mythgallery mythgame mythmovies mythmusic mythnetvison mythnetvision-data mythnews mythvideo mythweather mythzoneminder myth-doc
Pin: origin deb.linuxmce.org
# If our local package uses the same version as elsewhere, we take the one we have locally.
It has the latest libxine1
So the problem is isolated to my MD. Should I simply change the preferences? I don't want to break anything that might depend on those preferences.
EDIT: of further interest is that the core has the latest libxine1 installed, but it's not in the cache directory. Hmm....