youtube not running in firefox, but works with internet explorer
when i open you tube in Firefox, it does not run the videos. however the same runs good with internet explorer. a few weeks back the videos were running quite good with Firefox also.
You can try to Clear Now the Cache, Cookies, and Site Preferences in Tools (Alt + T) > Clear Recent History as well as Delete all in the Windows Control Panel > Flash Player > Storage tab.
If you have security software (antivirus, firewall etc.) installed, you can try deleting all existing instances of Firefox and its related files in all the different configuration areas/modules of the security software. Instead create new allow/trusted rules for Firefox + its related processes. Even otherwise the security software may also ask again when Firefox is started and you can try to allow/trust at that time. Please see this.
You can check for problems caused by a recent Flash 11.3 update and possibly downgrade to Flash 11.2 or 10.3.