Did you run the Flash uninstaller?

Troubleshoot Flash Player installation for Windows: http://kb2.adobe.com/cps/191/tn_19166.html

Flash Player uninstall: http://www.adobe.com/go/tn_14157 (this will remove the Firefox Flash plugin and the ActiveX control for IE)

You can also try to cClear the Flash cookies and settings.
Flash Website Storage Settings panel:
http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html

See also Flash Local storage settings
http://www.macromedia.com/support/documentation/en/flashplayer/help/help02.html

I did use the uninstaller. I had Adobe Flash Player 10 and a Shockwave Flash Plugin 10 so I uninstalled both, thinking there might be a conflict, then I uninstalled Firefox. I rebooted and installed the latest version of Firefox, then did a manual install of the latest Flash Player Plugin.

I cleared the cookies in Website Storage Settings and noticed that it shows None for the Website Storage Setting. After clearing those cookies and visiting Hulu, the list of visited sites is still empty. I don't know if that is normal.

Before I upgraded to the newest version of Flash I had options for local storage and I believe it was set to 100kb, but now I only have tabs for Hardware Acceleration, Microphone, and Camera with Flash Plugin 10.1.

I installed Flash for IE and in RealPlayer and both of those have no problem playing video with sound. Still no sound in Firefox.

Any other suggestions?

Hello and thank you for attempting to help. I was not able to hear any sound after hours of troubleshooting, so I decided to wait until a new version of either Firefox or Flash was available that I hoped would fix this glich.

I installed Firefox 3.6.12 using the upgrade option and now I have sound again. I think they fixed the glitch.

Thanks again for trying to help, cor-el.