Tvheadend

A few weeks ago I installed the latest stable tvheadend and it works well so far. When I set it up again I mapped all channels, but later on I found some more channels on frequencies which don't normally work during the day (which interfere with DVB-C), when I tried to map those to channels, nothing happens. I see 0/0 for a moment, then just an empty bar, and sometimes the window doesn't even show up and it just reports 'comet failure [e=Cannot set property 'innerHTML' of undefined]'.

The channels are enabled when using map selected. Map all doesn't work either.