For a good while, audio sharing issues plauged my Ubuntu workstation. Whenever I'd hit a website that used Flash 9, none of my other audio applications would be able to access the audio device until my Gnome session was restarted. Googl'ing around for Ubuntu and Flash, I stumbled onto this package, which I'm happy to say solved the issue.
Obviously, you can install it quite easily with apt.
sudo apt-get install libflashsupport
Hope this helps somebody.