I think he means 'add a known-working mux manually, and let auto-discovery work out the rest of them'.
Alternatively, pop over to #hts on Freenode and ask there... we have a few German users, it's quite possible someone is using DVB-C even if they're not in the same area as you.
That said, the only time I've seen the 'bad file descriptor' is due to a dodgy tuner connection, a lack of power to the tuner, the tuner going onto power-saving and not waking up, etc.; that's likely to be an OS-level message that the /dev/dvb/xxxx files are no longer accessible, even if they were when tvh started.
