I am not using linuxmce yet, but VDR
IIRC - it looks like the signal from your DVB-S (assuming satelite) card somehow was/is not allways good enough. And it seems that the xineplugin (or what ever is used in linuxmce to show the picture) does not recover after that.
Is the picture OK again after you switch channel (same or another and then back) ?
Is the sattelite antenna (or whatever you use) giving an OK signal ? Was it raining or something so that the signal was disturbed ?
If you can read german you could try searching www.vdr-portal.de
for more on this ...
I am looking into using LinuxMCE, and will ask some VDR-questions in the next days. And maybe you are the right man to answer them