When I last synced, my Zune removed 150 tracks. I didn't make any changes to cause so many to be removed from my devices.
After digging through my collection, I found that Zune "forgot" many tracks were part of my collection. The files were (luckily) still on the hard drive, but they were removed from my collection. Zune was given ample time to re-add them itself while it monitored my folders, but nothing happened. I manually added the folders, and it is currently putting over 800 tracks back into my collection.
Why would this happen? Why would the missing tracks be so random (some tracks on one album would be in my collection, and others on that same album would not)?
On a related note: back up your music files! If my music files were somehow wiped out without me knowing, and I just connected my Zune to the PC, the tracks would be lost for good!
Master Blaster (Halo 30), Rumble (Blue 8), Frenzy (Black HD 16)