Sound drop out on Bluray Playback

Hi, hope someone can help, bought my first Bluray player last week Samsung BD-P1500 connected to a Pana TX-37LZD70 with a Monster 750HD HDMI cable.

Tried about 6 Bluray discs so far, and all have suffered from an intermittent sound dropout (no sound for between 1&3 seconds) about 3 times per disc, what could cause this? standard DVD's are fine.

I've been in contact with Samsung and they'd not heard of the problem but are sending me a firmware update disc.

Thanks