A few weeks ago I saw some loop in Mythcommflag. The same movie was executed again and again and 10+ processes were running at the same time. I killed them all and restarted the MD; problem solved. After that Mythcommflag is running as it should.
I recall there is a parameter in the MythTV setup where you can control where the Mythcommflag job is executed, though I cannot find it now.
Some googling revieled this that could be worth looking at:
1) Set max number of jobs to 2. The CPU is dual core and has
hyperthreading enabled, and it handles this without flinching.
2) Enable the ""experimental speedup of commercial detection" option.
With those two settings, I've more than tripled my commercial flagging