UN40F6400AG with HT-F4500. Problem with ARC sound.

[guilherme]

After updating my TV I started having problems with the sound, which randomly stops working on the Home Theater connected through the ARC HDMI. Sometimes I will turn the TV ON and the sound will be working normally, but most of the time, even with the TV detecting that the Home Theater (Anynet+ Receiver) is connected, there will be no sound exiting through the HT speakers forcing me to turn it off and listen through the TV speakers.
Anybody could help me with this?

My current TV firmware is T-MST12UABC_2139.1