There appears to be some trouble in the land of Uverse so as a test, set the Uverse box back to 720p.
Also I don't know if you have the option for some optical from the land of Uverse to something else.
My audio cuts in and out on HDf channels only. The higher the channel number, the worse it is. I have U-verse cable. This problem has been occurring for several months. The cable box/DVR has been replaced, and I've switched HDMI cables to no avail. And I switched a HDMI cable from another HD TV that was working perfectly.The problem is present when using the TV speakers or when using the Onkyo surround sound amplifier. I've tried using the audio outputs from the side of the TV, too, nothing works. If I switch to the standard definition channel of the same show, the sound is fine. No problem with sound from my Sony PlayStation when playing Bluray movies. No problem on my other HD TV hooked to U-verse. The sound cutting out also is present on recorded cable shows. My Samsung is 3 years old and has a GREAT picture, but the audio is driving me nuts. Any ideas??