We got 'upgraded' to a V6 box a few months ago, and whole it's definitely better than the old box, it has been plagued with a few problems recently.
1. When trying to play things via the Netflix or Amazon apps, the screen goes completely blank and I have to reset the box in order to get them working
2. On BBC1 HD (ch.101), I'm having two problems - the sound is completely disappearing and can only be brought back by flicking the channel up and down, or the sound is occasionally 'robotic' and has what I can only describe as a 'metallic' sound to it.