Comment 138 for bug 439163

sorry, false alarm. Just in case this happens to anybody else, my issue was that some channels on a specific multiplex (perhaps the whole multiplex?) had moved to a different multiplex. Mythtv still had the old entries of channels in mysql even after clearing all channels and doing a full re-scan using mythtv-setup.
After wiping all entries from the channel table and doing another channel scan, things are working again now.
I kept thinking it was something related to mythtv tunning but it was just some confusion due to old channel entries in the database.