Since users started reporting the problems shortly after midnight today, many commenters guessed it was related to the fact that 2008 is a leap year. According to a post on the zune.net forums, they were right. Supposedly, the Microsoft engineers investigating the problem say that the capsized Zunes will right themselves automatically once the clock rolls over to Jan. 1. If that's the case, it may be best to wait for tomorrow, rather than disassemble the player.
If the post is accurate, this is a one-day inconvenience for Zune users that will soon be over. It's also an embarrassment for a player that's struggling for market share against Apple's iPod clan. Happy New Year, Zune users!