Same here. Called support, and here was my experience:
First couple of minutes I navigated the voice-response tree until I got to an agent. After some discussion (yes, I did all the recommended steps, and no I didn't open the unit...) they set me up with a return at no charge. My unit is out of warranty, but they are making it right anyway because it's not anything I did. Agent was friendly and to the point. Not too much runaround or convincing required - a nice surprise.
They will be sending me a box for returning the unit, and in 9-15 days I will have a repaired or replacement unit. I will have to re-sync my content, but that's no prob as it's all in my zune collection anyway.
On a scale of 1-10:
Zune freezing = 0
Support experience = 10
YMMV