Cannot hear internet audio (Jango/Pandora) on Mozilla Firefox but can on IE. What causes the incompatibility as I usually can?

For several years I have been listening to Jango or Pandora. For the past 2 on Mozilla Firefox. Suddenly I could hear no audio from either. I can hear audio from itunes or the media player but not from internet sources including youtube. After a day I had an epiphany and tried IE. Jango plays loud and clear. What is causing the incompatibility with Firefox? Where do I look to repair the connection?
Okay, nevermind. I went to Mozilla Firefox and found out that several (4 or 5 were out of date) of my plugins need updating. I did that, it being quite easy updating all from one page. Restarted and Jango plays. Amazing grace.