Go to Tools and select Options (or Firefox Button and Options..), click the Advanced Tab. Inside here click the General Tab and deselect "Warn me when web sites try to redirect or reload the page" under Accessibility.
You may see if whitelisting YouTube for NoScript helps.
You could also try disabling/enabling Auto-reload:
In a new tab type "about
:config" and search for "accessibility.blockautorefresh".
To block it - set it to true
To unblock it - set it to false.
You may also have a third party addon corrupting YouTube on Firefox.
You might also see if this helps: https://addons.mozilla.org/en-US/fir...efreshblocker/