after Channelscan the channeltable cannot be edited in Mythweb
When doing a channelscan in mythtv it usually creates a large number (500+) channels -at least on DVB-S. When the channeltable is being displayed in Mythweb after that, channels cannot be edited anymore. In order to do that, /etc/php5/apache2/php.ini needs to be changed. The variable max_input_vars needs to be added and set to an appropriate value. I arbitrarily set it to 10000, restarted apache2 and its working nicely.