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.
Study the clip at 28 seconds in. You'll see that the display is working fine before the white mask flashes back in. While OLED engineers in the audience can feel free to correct us, we think there's a strong possibility that the problem is software-based (and thereby firmware-fixable through a patch). But obviously, make Microsoft give you a new Zune right away if you're encountering such an issue.