I had the same problem. I simply uninstalled 11 completely off my computer. Then went to itunes.com and re-downloaded it. In your music folder there is a folder "iTunes" and in there a sub folder named "Previous iTunes Library." When you uninstall iTunes from your computer this folder remains put and is what retains your music library when you re download and install iTunes.
I never use playlists so I wouldnt know if your playlists are saved.
This is how it worked for me, I'm sure there are other solutions to the problem but this is the route I took. Hope this helps!