two firefox questions

1. I have a linux centos machine.  There is no audio card.  I was using Logitech USB headphones.
    Worked fine.  Then I found Logitech USB speakers and switched.  Works pretty well.  I just notice
    though if I use firefox with audio (e.g. via youtube) and then am done and later want to use xine
    xine won't work unless I exit firefox and pkill it because firefox seems to have the audio for itself.
    It is not even enough just to close the youtube window.  Am I stuck with this?

2. We have two networks, a 192.168.5.X network and a 10.X.X.X network.  Only the 192 can access
    the outside.  My desk is on a 192.168.5 network.  If I want to access something in the lab I have to
    ssh -X to 192.168.5.15/10.0.0.215 and run firefox there.  Similarly if I am in the lab and want outside]
    access I have to ssh -X to 10.0.0.215/192.168.5.15 (same machine, I just switched the IPs) and run
    firefox.  Problem is, say I am at my desk and ssh to that machine and then run firefox.  Later I am in
    the lab and ssh to that machine.  I try to run firefox and it says it is already running and I must first
    kill it before I can bring up a session.  Then it kills the one from my desk.  Isn't there a way to run
    multiple firefoxes without having to kill the one to start another?