Great work! Linux users now officially love you :-)
edit: just tried the site in Firefox ; can't even get the sign-in form to react. :(
Seems OK in Chrome, but at least the Flash version worked in FF for me.
We tested pretty extensively in Firefox, but there's always things that can go wrong. Also if you think you have any info that will help us fix it, hit up the Contact Us link at the bottom of http://help.grooveshark.com/
So, on the one had, the trouble is at my end, but on the other hand most sites have no trouble with my add-on arrangements, so there's something that's at least a little sensitive in the GS scripting.