I'm getting this as well. In addition to the whole screen going black for a fraction of a second I'm also seeing some flickering horizontal black lines appear if there is anything bright red in the picture.
i messaged a virgin operator about this and got told off for contacting them directly by a moderator ....wrist slapped well if they didn't give us faulty equipment i wouldn't be spending my spare time contacting them..
I had this problem a month ago on various channels, engineer came out, change a few things. He had not heard of the problem before suggested it could be a setting on my TV (Samsung). No problems until this evening watching 4HD black screen for a second or 2 very intermittent. BS35 Bristol area