So, it turns out that if you don't sign into the Zune marketplace for 30 days, all of your DRM'd content expires. I got a new 64 GB Zune HD recently and couldn't figure out why it was loading so slowly. I usually just sync my Zunes when I'm home, because my work laptop (which travels with me) runs Windows Server 2008 R2 and I never thought it was a big deal to just synch with one of my personal machines when I was home.
Despite the fact that I subscribe to the marketplace on a quarterly basis, it would seem that when you download music from the marketplace, it is *always* tagged with a 30-day expiration.
Long story short, I took my Zune HD on the road with me and installed Zune software on my WS08R2 machine (which is completely unsupported and something you should not do), and when I finally had a few minutes to dig into my collection, I found that the reason that the Zune was loading slowly was because all of my rights had expired and something wasn't working when it came to updating them. I tried various things to fix this, and finally found something that worked. I fired up Windows Media Player, which is configured to automatically download my usage rights, and I let it update my library. Voila! The Zune software now recognizes my rights to the songs and is churning away at putting them back into my library.
So, don't do what I did. Specifically, DON'T:
1. Fail to log in to the Zune marketplace for more than 30 days.
2. Install Zune on an unsupported platform
3. Use the Zune software to purge all of your subscription content and tell it to re-download everything.
But DO let Windows Media Player fetch your use licenses for you.