Your 1st Generation iPod Nano is Prone to Overheat, Apple Says
"This issue has been traced to a single battery supplier that produced batteries with a manufacturing defect," Apple said in a statement. "While the possibility of an incident is rare, the likelihood increases as the battery ages."
Affected iPod nano devices were all sold between September 2005 and December 2006, and if you own one, Apple recommends that you stop using it immediately and a order a replacement, on Apple's dime. That's the good news. The bad news? If you own a personalized iPod nano, the replacement will be a non-personalized unit.
You can order a replacement on the Web by visiting here (don't forget to backup your data first).