Unfortunately, not really. Your iTunes preferences must have gotten fubbed up in the update for some reason... it's really odd.
Your iTunes playlists are stored in the "iTunes 4 Music Library" file located in your Music folder. (I believe) Well.. I tried deleting the iTunes preference file.. and it didn't affect the Playlists in iTunes.. only where the songs were stored.
I'm not sure you will be able to get them back.. but someone else may have a better idea.
Just go to your iTunes Prefs and make sure Manual update is selected, rather than Auto Update. Then you can configure all of your music/playlists again. It's a real pain... I know. I went through it when installing Tiger.
Happened to me too during recent s/w update. Was not willing to accept loss of all libraries so called Apple tech support. Apparently it happens to many 'customers' during s/w update. Anyhow, by not taking 'it can't be done' for an answer they escalated my call to the application specialist in Texas. He had a simple fix. Go to your user/music/itunes/previous iTunes Libraries folder. The s/w update tucked a copy the various indexes there. You can copy the 'iTunes 4 Music Library (old)' file up one level to the iTunes folder and rename to get rid of the '(old)'. Should fix the problem. Caveat: i did this a month ago and above is by memory, i didn't think to write down the steps at the time. Good luck.