Can not view videos on you tube in firefox4 using flash player11

I'm using firefox 4 and i can not view videos on you tube.I've updated and reinstalled adobe flash player twice with no results.I've also tried the other checks,security blocking,cache,pop ups etc Works fine on IE. Hope someone has a solution.I've always liked firefox but not the newer versions and many of the changes;

I can't believe you're still running Firefox 4. Why not a newer version?
There are a number of active threads concerning the latest Flash player plugin (11.3) and the latest Firefox (12-13). Not all users are experiencing the same issues, but things to check include the following:
- Conflict with Realplayer Browser Record plugin (to disable this, open Add-ons from the orange Firefox button or the classic Tools menu and look under the Extensions and Plugins categories)
- Conflict with Flash 11.3 Protected Mode (see [ Adobe Forums: How do I disable Flash Player's protected mode for Firefox?])
Scanning down the front of the forums probably will yield additional suggestions:
Does any of that appear promising?