Hmm. It works for me in Chrome but not in FF. I need to do further testing because there are other factors at play (i'm not logged in in Chrome). I'll get back to you in a few.

Edit: interesting. I changed the icon, went back to Chrome (still logged out) and it wouldn't work any longer. cleared cache, refreshed it, it worked again but not consistently. I keep going back and forth between this comment in FF and Chrome and sometimes it work and sometimes it doesn't. It sort of looks like that if you hover again too soon the hover text won't show. Not sure, though.