It's been working fine for me as well. Do you have a another PC or friend that can run what you are on FireFox and see the same issues exist?
EDIT: Sorry, I basically repeated what Ashley said.
Also, I noticed on my laptop if I have a music player running at the same time and then stand by my laptop and restart,it causes funny sound noises like you described.
Also, see if there is an update on your sound driver