iTunes 11.1.3.8 update" Deleted playlists

I'm running Windows 8 (64 bit) and just updated to iTunes 11.1.3.8.

While the songs are accessible, ALL of my playlists are gone. Ten years of playlists, gone--including an 8-hour list for Christmas Day.

I've tried replacing the "iTunes Library" file with an older version--this didn't appear to change anything.

All of the iTunes materials are on an auxiliary hard drive. iTunes worked fine--on two laptops--until the update. Now, the playlists are gone on both laptops, so the update affected the files on the auxiliary drive they run from. Because I synched my iPod this morning to get newly purchased songs, all of the playlists are now gone from the iPod, too. (My iPod is a 6th generation Nano--model MC699LL).

How do I fix this?