You can probably recover your playlist. (Instructions for Chrome)
On the computer you used grooveshark on: visit the website, open developer tools, open "resources tab", click on local storage->grooveshark.com. Now find the key called 'libraryXXXXXX' where the X's are numbers. Right-click it, "edit value" and copy/paste that data here: https://json-csv.com.
I just made an account on this site so I could tell you this, but you just saved the last four years of my music collection. I can't tell you how incredibly thankful I am right now.
I just made an account also only to tell yuo that I am incredibly grateful for your help, my music is really important to me and you just saved my several-year collection. THANK YOU!!!
Late, but if your library gets truncated because it is huge like mine, you can instead get it by opening the console and typing JSON.stringify(localStorage); while on grooveshark.com
On the computer you used grooveshark on: visit the website, open developer tools, open "resources tab", click on local storage->grooveshark.com. Now find the key called 'libraryXXXXXX' where the X's are numbers. Right-click it, "edit value" and copy/paste that data here: https://json-csv.com.
Source of instructions: http://www.reddit.com/r/Music/comments/34goss/meta_groovesha...