i wonder if anyone just did a windows update?

i could play it fine, in fact i was or had just used it before doing an update since it had been ages.

upon rebooting firefox no longer would play youtube videos's, explorer does it just fine so something i'm thinking in the windows update (not a firefox update) changed something disabling firefox from being able to play them.

I have the same problem. I just started today as I did not have any problems yesterday. I suspect there's something wrong with YouTube site. I have tried Chrome and IE8, same results, couldn't play the videos. Only a black screen. I have deleted cookies and cache and still won't work. I guess I'll wait for a while to see if it comes back.

ok a couple of things

try reinstalling adobe flash player i did that even though it said i had it installed and had the latest edition.

even after that they still would not play, just a black box as this post that started said(however i could play them just fine in explorer).

anyways if that don't work you can reinstall firefox and that probably will fix the problem.

i do have to add a note onto that as i didn't reinstall the latest version of firefox like i had but did the beta version, but i'm thinking the other one would work too and fix whatever setting was changed, i'm still blaming the windows update i did.

now i would go back to the other firefox if i dind't have a problem getting the beta set up the way i like it,

tabs on top, omg that was annoying, and i can't move my home button to where i want it, but thats probably due to the theme i am using.

i've gotten stuck on this theme ages ago and now anything else looks odd and i've had to over ride its compatibility since version 3 of firefox.

but i have everything the way i like except for the home button

so try reinstalling your current version of firefox, i am not sure why i didn't start with that.

ok

just reinstalled the lasted non beta and youtube is playings till just fine.

i had to check out a few things i thought i had lost in ver 4 but it appears i did nto have them in my current version either, probably due to using a theme that hasn't been supported since version 2 something.

just for those who are thinkign about upgrading to the beta a few things.

tabs by default are on top but you can change that,

if your theme is not supported and you over ride it you might have problems getting everything back to where you like it, like the home button now is default on the right side of the address bar

the top bar makes no sense, its all blank except for a ribbon line box, but you can change that to show the menu bar again, i just don't see why its like that unless its not a finished feature.

they say the drop down menu by the back button is gone but i can say i didn't have it but i don't have it in version 3.xx either probably due to the theme

but the biggest thing and this si going to keep me from going back to version 4 until its fixed is the saving and closing. there is no option to save and close in 4 only to close it.

I'm not using the beta version but 3.6.15 , but I am having this problem. I already reinstalled flash and rebooted a few times to now luck. I think it may be a problem with youtube's site.

http://www.youtube.com/swf_test.html plays the video fine with no problems, however if you click on the video to view it 'on youtube' I get the black box. http://www.youtube.com/watch?v=SHZFsJKlsuA&feature=player_embedded

Here's my latest update. I reboot my PC and now YouTube is back. I am not sure what is the problem. But I do think it's YouTube website since videos did not play with all three browsers (Firefox, Chrome and IE8). And I haven't changed anything in my PC or install any new add-ons.

If you still have the problem, try to reboot your PC to see if it works, before you reinstall Firefox. Now YouTubes videos play normally again in all three browsers.

Just found an answer that worked for me on the youtube forums, if you change the http to https it let me view videos on youtube.

Had the same problem. Adding the s to http fixed it. Now the question is why did this suddenly happen and will I have to manually adjust the URL every time?

I am also having a problem with my Firefox. I have rebooted the browser and rebooted my system. All my problems began when I upgraded to 4.0. No youtube videos and each tab takes forever to load now. Plus now it constantly freezes up on me. I have to open my Safari browser but not all things work on their, like watching Netflix movies (which is also not working since the upgrade). I want to go back to the 3.0 level.

Win 7 updated and now YouTube will not play

My issues started after I received an adobe update. I have read many solutions, but none of them have worked. Does Mozilla have a fix for this problem? Also, it's not just youtube videos that are not playing on firefox. None of the sites that I have gone to play either.

If disabling the RealPlayer extension did not work, can you please try uninstalling RealPlayer completely from the Windows control panel? This issue may be a bit more involved than just the one extension.

So here's what I'm running. Windows 7 on a Dell inspiron 14, about 2 years old. Untill a few days ago my FF was working fine, then on all of my programs (FF, Chrome, Safari, etc.) just stopped playing youtube and any other videos around the net. Finally I got it to work on the others but not FF and it's really pissing me off. I've uninstalled a bunch of unnecessary programs, uninstalled FF and reinstalled it as well as reinstalling Flash player to FF, still doesn't want to work. Now I'm at the point of rebooting my entire computer. Please help.

Thank you so much! Your advice worked for me! After toiling over this issue all day...I can now play internet radio, you tube videos, etc! Thanks so much for the tip!

I had the same problem and was able to easily fix it by following co-rel's suggestion in another post by going to this link http://forums.adobe.com/thread/1018071?tstart=0. Now all of my browsers are playing the videos again. Amy

So I have the same problem still but now on youtube it was saying I need the newest flashplayer, but I tried installing the newest version again and still I got that message on youtube. I tried uninstalling FF 13 and installing FF 3.2 to see if the older version would work but 3.2 only flash 10.2 works and not flash 11 so I'm in a corner.

Disabling the realplayer record/download function actually worked. Funny how realplayer and Firefox seem to have conflicts often. Thanks for the solution @ Matt G.

Same problem. My other computer is on Mozilla v13 as well but using XP and it works fine but hellishly slow.

well, it could be YouTube. see if maybe a YouTube technician can help. i think it takes someone with computer skill to help. someone tell mozilla to make an update for this. maybe it is a bug. it may not even be mozilla's fault!