Your description sounds like the way VDR used to work. It the latest incarnation (well, already a couple of month old), VDR is using a different approach on the MD. vdr is started on the MD when you click on TV, and stopped when you exit the TV application.
Try apt-get upgrading your hybrid, recreate the diskless image (/usr/pluto/bin/Diskless_CreateTBZ.sh), and recreate the MD in question.
Good luck.