bNormal........I have exactly the same problem....My config is as below
Pioneer-HTP-071, its 4 HDMI inputs are all connected, and the HDMI out is connected to LG LM7600's HDMI1 port. Read all manuals, jiggled all wires, sometimes, Audio from TV (I used a USB Key on the TV to play some music) plays flawlessly, othertime, it starts and then stops, and starts again and stops...very annoying...but the sequence as recommended in the Pioneer manual for ARC to work is...
1. TV should be with ARC on, Simplink On
2. Turn receiver on first and then the TV.........other sources connected to Pioneer should be off, but this may not be required, as long as Pioneer is set to 'TV'
The above is supposed to work...but don't know why the audio goes on for about 2 secs, and stops for 5 secs and so on.....at times, it plays flawlessly :-( Don't know where to start the debugging....and just saw your post....so, thought I would comment