"It's tough to know just how often this particular problem is occurring, but we've heard a fair share of reports on the Zune HD's otherwise gorgeous OLED display having performance glitches. And needless to say, you'd notice it. Here, the touch controls are 100% intact; the problem is that the bottom majority of the screen is completely washed out in a bright, white filter."
We'd heard about the non-responsive screen issue last week, but this one seems to be unrelated. A white mask shows up over the lower half of the screen (it appears to cover everything but the "breadcrumb" navigation area of the interface.) As Gizmodo points out, at 28 seconds in it appears the colors show up normally, lending credence to the theory that it's merely a firmware-based glitch and can be fixed in a future update.