I just woke up this morning and exactly the same thing!
Last 2 days it's been perfect, last night perfect, get up this morning, no sound, no picture!! I've done a full reset, and still nothing, so looks like I'll be sending mine back as well! This will be the 2nd time I've returned it, so will now be on my 3rd unit! A little dissapointed must say, but that's electronics I guess! :/
And just as a side note, in comparison to last night, it takes 5 times longer from when I press the power off button, for it to actually turn off! Is this a sign of something particular going wrong?
I had the problem of not being able to connect itunes or iPhone over airplay even though the network connection was fine (Iphone app worked perfectly). All I did was pull the plug out of the back for ten seconds, and it fixed it. SO that problem was solved thanks to a member here on the forum! (Thanks!)