Nano 2nd Gen Not Recognzied

My iPod Nano 2nd Generation is not recognized by my computers: a MBP with 10.7 or iMac with 10.6. The Nano says it is charged, but does not show up in iTunes, Finder, or /Volumes/. Yes, I've tried multiple cables, including the original one (with the thin end).

iPod Nano 2nd Gen

Version 1.1.3

Model MA497LL

iPod itself works fine, I just can't update it on either computer. Any suggestions??