Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Thanks, clearing cookies for YouTube did the job.

Same issue. For me it started slowly. At first I could refresh the page then i can post. Now can no longer refresh the post then post.

I cleared all cookies, the cache. Still nothing Then turned off all add on's. Still nothing Then went into Firefox safe mode. Still nothing

EI still works so I can not figure this out.

Thanks

I have the same problem. I can't submit comments and get an error notice. I can type them in, but can't send them. I also can't like/dislike videos as well as put them into any of my play lists.

Is it a plug-in error or something?

I am having the same problem, I can post comments to Youtube on my Smartphone, I.E 9.0 and even on Chrome, but when I do it since updating to the latest Firefox 21.0 it gives me a error message when I click post every time! Obviously a bug? its the same for the thumbs up or down.

I tried restarting Firefox in Safe mode and then went and commented on a video and whalla it actually worked.... so then I thaught it must be a plugin problem.

I disabled all my plugins then re-enabled them one after the other until whalla I found the culprit!

The error is in the DownloadHelper 4.9.14 Extension Plugin, hope the Authors of this plugin are reading this, it is causing users commenting and posting errors in Youtube and needs to be patched!

Hope this helps others!

cor-el's answer solved the problem for me. YMMV

The Video DownloadHelper 4.9.14 extension also has been reported to cause such issues on the YouTube website.

If you have this extension then try to update to the 4.9.15 version that has been released to address this issue.

• https://addons.mozilla.org/firefox/addon/video-downloadhelper/#detail-relnotes