I have trouble with my TV.

I just bought before a month a SC-HTB20 2.1 Sound System. It is connecteed over HDMI ARC to my TV.
It boots and shutsdown together with the tv. I can also control the volume with the tv remote as i expected.
So i was really happy.

Setup:
7606K02 55 FW 14.101 & 14.9X
Im using the internal (analoge & digital) cabel reciever of my 7606K02 55 to watch tv. I also have a PS3 Slim and a Unitymedia Recorder, and a Networkcabel conneted to the TV.

Problem:
While watching TV Playing PS3, Streaming to the TV the sound drops. That means that the sound of the 2.1 system comes only frome the right speaker and really silent. I have to change the audio channel of the TV station, or switch the channel, or mute and unmute multiple times to get the sound back. This only happens on Digital channels, especially on ARTE HD.


I tried alot to get rid of it.
Factory Reset of the TV,
unplugged everything including network and HDMI devices except of the 2.1 system on HDMI1 ARC.
Switched the HDMI cables between TV and 2.1 System (tryed 3 different brands with 1.4 standard).
without a change.


Any ideas what can i try? Some one else with such problems?