Try to set the Flash plug to click-to-play by setting the permissions for Flash to "Ask To Activate" in "Firefox/Tools > Add-ons > Plugins". That way you can activate the Flash plugin when you need it via the Lego block icon on the location bar.

it looks like user.js is currently active in Firefox. The user.js file is only present if you or other software has created this file and normally it wouldn't be there.

You can delete a possible user.js file and numbered prefs-##.js files and rename (or delete) the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in the current Firefox release. You can get to the profile folder below:

• Help > Troubleshooting Information > Profile Directory > Show Folder

or

• Go to about:support and click Show Folder next to Profile Directory.

Can you try to start Firefox in Safe Mode to see if Firefox works properly with no error? You can start Firefox in Safe Mode below:

• Windows/Mac: Go to Help > Restart with add-ons disabled
• Linux: Run firefox -safe-mode in the Terminal/Konsole

If Firefox opens up fine with no problems, it's probably one of your extensions that's causing the issue. You can re-enable your add-ons one by one until you find the one that causes the issue upon being re-enabled.

The ask to activate only brings it back to the black screen, no change. I noticed that I ahd two Shaockwave Flash Plugins, one 12.xxx the other 13.xxx. Could this be a problem?

The middle part of your answer is completely baffling to me but I"m not sure I want to get rid of all my preference settings. I'm not sure how I got them as they are now, which I like, and everything is working fine except for the Flash video on some pages since the update.

In the Profile folder I find: prefs prefs.js.bak prefs.js.new prefs-1 prefs-2 prefs-3

User User.bk

What do you suggest I do with these and what will happen if I do it? Also, would any of these have anything to do with flash video not playing your tube videos due to Firefox updating to 29.01?

Restart in Safe mode (no add ons) did not change anything.

The ask to activate only brings it back to the black screen, no change. I noticed that I ahd two Shaockwave Flash Plugins, one 12.xxx the other 13.xxx. Could this be a problem?

Yes. Remove the 12.xxx version.

  The middle part of your answer is completely baffling to me but I"m not sure I want to get rid of all my preference settings. I'm not sure how I got them as they are now, which I like, and everything is working fine except for the Flash video on some pages since the update. 

Basically a program or you creates a user.js file that alters some aspects of the browser. You can see more information about the user.js file at http://kb.mozillazine.org/User.js_file

   What do you suggest I do with these and what will happen if I do it? Also, would any of these have anything to do with flash video not playing your tube videos due to Firefox updating to 29.01? 

Delete them. If you have a prefs.js file, delete that to reset all prefs (from about:config). More information here: http://kb.mozillazine.org/Prefs.js_file
At times, the user.js can be a problem as some programs write it in to change your home page and others when you get adware.

What troubleshooting steps have you tried? Have you disabled hardware acceleration in Flash and Firefox? Did you disable protected mode in Flash? Did you create a new profile as a test?

I'm not sure how to remove the 12.xxx version,. I don't understand why it is there, usually updates over wirte the old one as far as I know. I don't know where to find it.

pref .js deleted. I could not find a user.js

I disabled hardware acceleration on one of them, not sure which and I don't remember how I did it but think it must have been on the flash. No idea what protected mode is no new profile, I've never done this.

Ok, did what you have said as much as I could. I have been fidgeting with things now for a couple hours. After doing a CCleaner and Registry cleanse, turning off and restarting the computer, the videos are now p-laying.

I would still like to know how to find and get rid of the duplicate Flash plug in though if you would't mind.

Thanks for the help.

I'm not sure how to remove the 12.xxx version,. I don't understand why it is there, usually updates over wirte the old one as far as I know. I don't know where to find it.
You can just uninstall the previous version through your Control Panel.
(Start > Control Panel > Uninstall a Program)

  pref .js deleted. I could not find a user.js 

prefs.js is fine. I swear user.js was active in your Firefox install. The troubleshooting information never lies!

  I disabled hardware acceleration on one of them, not sure which and I don't remember how I did it but think it must have been on the flash. No idea what protected mode is no new profile, I've never done this. 

You can check which one you disabled by visiting their options.

To check if HA is disabled in Flash, do the below steps:

1. Go to this Adobe Flash Player Help page.
2. Right-click on the Flash Player logo on that page.
3. Click on Settings in the context menu. The Adobe Flash Player Settings screen will open.
4. Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
   
   The image "fpSettings1.PNG" does not exist.
   
5. Is the box labeled "Enable hardware acceleration" checked or not. If it is checked, HA is on. If it's not checked, it's off.
6. Click Close to close the Adobe Flash Player Settings Window.

Also, you can see if Firefox's HA is disabled by below:

• Click the menu button and select Options for Windows or Preferences on Mac or Linux. For Firefox 28.0 and previous versions, click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options.
• In the Firefox options window, click the Advanced tab, then select "General".
• In the settings list, you should find the Use hardware acceleration when available checkbox. Is it unchecked or checked? If checked, it's on, unchecked, off.
• Now, restart Firefox and see if the problems persist.

You might want to switch off Flash player's hardware acceleration and run it for a while to see if it crashes still.

OK, Both have HA disabled now.

I think the Flash 12.xx is a phantom. I can't find it on my comp. Only 13.xx shows anywhere but on the Pugins page in Firefox.

About the .Js I cannot find a User.JS in the profile folder but ther is a user.bk and other files that have.json. Should I do anything with these?

extensions.json search.json search-metadata.json sessionCheckpoints.json signedInUser.json times.json

    I think the Flash 12.xx is a phantom. I can't find it on my comp. Only 13.xx shows anywhere but on the Pugins page in Firefox.

Weird. I don't have any clue why it does that. Your System Details list only shows Flash 13.0.r0.

   About the .Js I cannot find a User.JS in the profile folder but ther is a user.bk and other files that have.json. Should I do anything with these? 

If you cannot find it, that's okay. Leave all files alone.

Does disabling HA in Flash and Firefox work better for you now or does it still not play?
Make sure your firewall isn't blocking anything from Firefox.
Does this happen in other browsers as well?

Does the following site display your Flash player version and your OS?

• http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

Here's what mine looks like

The Video started playing on You Tube before I disabled HA in Firefox.

One of the first things I checked was firewal and then turned off adblocker for the page. I forgot to tell you that when you asked what I had already done.

I don't use any other browser.

That info is correct.

I think it is working now. Thanks for all the help.

Glad to hear it's working again. If this problem arises again, please reply back to this post and we'll start working on it again.