In order to be able to find the correct solution to your problem, we require some more non-personal information from you. Please do the following:

• Click the Firefox button at the top left, then click the Help menu and select Troubleshooting Information from the submenu. If you don't have a Firefox button, click the Help menu at the top and select Troubleshooting Information from the menu.

Now, a new tab containing your troubleshooting information should open.

• At the top of the page, you should see a button that says "Copy text to clipboard". Click it.
• Now, go back to your forum post and click inside the reply box. Press Ctrl+V to paste all the information you copied into the forum post.

If you need further information about the Troubleshooting information page, please read the article Use the Troubleshooting Information page to help fix Firefox issues.

Thanks in advance for your help!

Also attempt to troubleshoot Flash's protected mode and all other methods of troubleshooting told on the link below.

• kb.mozillazine.org/Flash#Troubleshooting

Thanks, here you go.

 Application Basics

       Name
       Firefox

       Version
       23.0.1

       User Agent
       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:23.0) Gecko/20100101 Firefox/23.0

       Build Configuration

         about:buildconfig

 Extensions

       Name

       Version

       Enabled

       ID

       Download YouTube Videos as MP4
       1.7.8
       true
       {b9bfaf1c-a63f-47cd-8b9a-29526ced9060}

       Pocket
       3.0.4
       true
       isreaditlater@ideashower.com

       ScrapBook
       1.5.6
       true
       {53A03D43-5363-4669-8190-99061B2DEBA5}

       Skype Click to Call
       6.11.0.13348
       true
       {82AF8DCA-6DE9-405D-BD5E-43525BDAD38A}

       StumbleUpon
       4.16
       true
       {AE93811A-5C9A-4d34-8462-F7B864FC4696}

       Xmarks
       4.2.3
       true
       foxmarks@kei.com

       Freemake Video Converter Plugin
       1.0.0
       false
       fmconverter@gmail.com

 Important Modified Preferences

     Name

     Value

       accessibility.typeaheadfind.flashBar
       0

       browser.cache.disk.capacity
       358400

       browser.cache.disk.smart_size.first_run
       false

       browser.cache.disk.smart_size.use_old_max
       false

       browser.cache.disk.smart_size_cached_value
       358400

       browser.places.smartBookmarksVersion
       4

       browser.startup.homepage
       https://www.google.com.mx/webhp?hl=en&tab=ww

       browser.startup.homepage_override.buildID
       20130814063812

       browser.startup.homepage_override.mstone
       23.0.1

       browser.tabs.warnOnClose
       false

       dom.mozApps.used
       true

       dom.w3c_touch_events.expose
       false

       extensions.lastAppVersion
       23.0.1

       gfx.direct3d.last_used_feature_level_idx
       0

       gfx.direct3d.prefer_10_1
       true

       network.cookie.prefsMigrated
       true

       places.database.lastMaintenance
       1377827154

       places.history.expiration.transient_current_max_pages
       104858

       plugin.disable_full_page_plugin_for_types
       application/pdf

       plugin.importedState
       true

       plugin.state.java
       0

       plugin.state.npdeployjava
       0

       privacy.cpd.downloads
       false

       privacy.cpd.history
       false

       privacy.donottrackheader.enabled
       true

       privacy.popups.showBrowserMessage
       false

       privacy.sanitize.migrateFx3Prefs
       true

       privacy.sanitize.timeSpan
       0

       security.warn_viewing_mixed
       false

       storage.vacuum.last.index
       1

       storage.vacuum.last.places.sqlite
       1377145732

 Graphics

       Adapter Description
       Intel(R) HD Graphics Family

       Adapter Drivers
       igdumd64 igd10umd64 igd10umd64 igdumdx32 igd10umd32 igd10umd32

       Adapter RAM
       Unknown

       Device ID
       0x0116

       Direct2D Enabled
       true

       DirectWrite Enabled
       true (6.2.9200.16571)

       Driver Date
       12-16-2010

       Driver Version
       8.15.10.2266

       GPU #2 Active
       false

       GPU Accelerated Windows
       1/1 Direct3D 10

       Vendor ID
       0x8086

       WebGL Renderer
       Google Inc. -- ANGLE (Intel(R) HD Graphics Family)

       AzureCanvasBackend
       direct2d

       AzureContentBackend
       direct2d

       AzureFallbackCanvasBackend
       cairo

 JavaScript

       Incremental GC
       true

 Accessibility

       Activated
       false

       Prevent Accessibility
       0

 Library Versions

       Expected minimum version

       Version in use

       NSPR
       4.10
       4.10

       NSS
       3.15 Basic ECC
       3.15 Basic ECC

       NSSSMIME
       3.15 Basic ECC
       3.15 Basic ECC

       NSSSSL
       3.15 Basic ECC
       3.15 Basic ECC

       NSSUTIL
       3.15
       3.15

Attempt Firefox safe mode and see if it occurs there...

• Diagnose Firefox issues using Troubleshoot Mode

Also try the flash troubleshooting as I said in my last post.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

NOTE: Install the SUMO Troubleshooter. This add-on will add your troubleshooting information that you posted above to all future questions.

I've got this exact same issue.

I've tried disabling Hardware Acceleration in both Firefox and Flash, I've booted up with Safety Mode enabled and themes disabled; videos will stop playing and will only play when I'm scrolling my mouse." It doesn't happen in Safari.

Running Firefox 23.01 Mac OSX 10.8.4 Flash 11.8. r800

I had this problem previously and tried everything with Flash and Firefox. Except it took me way longer than it should have to try the most obvious thing, which fixed it:

Update your graphics/video card drivers.

This may or may not be your problem, but it's worth it to try.

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows:
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back soon.

I'd actually already tried reinstalling earlier, and used CCleaner to make sure I got every last bit. Aside from re-syncing with my Firefox account after installation, it was a fresh start. Still didn't fix the issue.

Also, in regards to updating my graphics card, I guess Macs auto-update your graphics cards with every software update. So I upgraded to 10.8.5, but I've still got the issue. Plus I'm not sure if that was the issue anyway; I know this is probably a naive statement, but if it was graphics card related, why would videos load fine in Safari but not in Firefox?

Review YouTube's permissions on this Firefox browser.

This can be done by clicking on the Earth/lock icon at the left side of the address bar.

Also, please try the following:

1. Go to the Firefox options
2. Select the Advanced tab
3. Select the Network tab
4. Click the Configure How Firefox Connects To The Internet button
5. Select Use System Proxy Settings
6. If this doesn't fix the issue, select Detect Proxy Settings For This Network

Please report back soon.

As far as Permissions are concerned, I allow Youtube to Load Images, Set Cookies, Maintain Offline Storage, Enter Fullscreen, and Hide My Mouse Pointer. I block it from everything else.

As far as proxy settings are concerned, it matches my System's proxy settings. Neither "Auto-Detect" nor "Use My System's Proxy Settings" resoles the issue.