You have 2 flash plugins, which causes issues, delete the pluginreg.dat file in your profile folder.

1. Orange firefox Button => Help => Troubleshooting => Open Folder (a new window with the file explorer should show)
2. Now close Firefox then delete the pluginreg.dat file.
3. Now open firefox again and try to load a video.

• More information (if youre confused) is at => https://support.mozilla.org/en-US/kb/troubleshoot-issues-with-plugins-fix-problems#w_re-initializing-the-plugins-database

Thanks for your prompt reply, but it did not solve the problem. Kind regards.

Jan

Try to install the last beta version of Video Download Helper.

• http://www.downloadhelper.net/install-beta.php?version=4.9.21a1

See also:

• http://bugzilla.downloadhelper.net:8080/show_bug.cgi?id=536

Thank you, but still can't play any video on Firefox. Regards.

Jan

Can you find a similar addon thru addons.mozilla.org . I know Youtube makes many changes that break these addons.

Did you remove both older Flash plugins and installed the latest version of the Flash plugin.

1. Shockwave Flash 11.7 r700
2. Shockwave Flash 11.6 r602

You can check the Flash player installation folder for multiple Flash player plugins and remove older version(s) of the plugin (NPSWF32).

• (32 bit Windows) C:\Windows\System32\Macromed\Flash\
• (64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\

You can find the latest Flash player versions for Firefox on this page.

• http://www.adobe.com/special/products/flashplayer/fp_distribution3.html

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

• Do NOT click the Reset button on the Safe Mode start window.

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

You can check for problems with current Flash plugin versions and try these:

• disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)
• disable hardware acceleration in the Flash plugin

• http://kb.mozillazine.org/Flash#Troubleshooting