I have same kind of black screens. I have only one FF dvb-c card, old fujitsu-siemens one. Sometimes I get image back by opening menu, sometimes I need to retune to channel, sometimes I need to retune to another transponder and most annoyingly sometimes I need to restart vdr to get image back.
I'm using dvd plugin, mp3 plugin and subtitle plugin (dvb, not teletext) and vdradmind. Marko
I have one budget card (Airstar2 DVB-T) and I had exactly the same symptoms. The picture disappeared always after an EPG scan - and never came back. I had to restart VDR to get the picture again. When I set "EPGScanTimeout = 0", it does not happen any more. I do not know how this helps, but it does it for me.
Kari