This might be a general "could not download" error that can occur with videos hosted by Brightcove:

Note: In general, PLAYER_ERR_TIMEOUT happens when the player expects to be playing video but can't make any progress for 45 seconds. This can be the final result of many things that happen earlier, including the suspension of the browser when a tab is put in the background, for instance. But it can be a sort of catch-all condition for network or platform conditions that prevent playback from continuing.

http://docs.brightcove.com/en/perform.../errors-plugin.html

Could you provide a link to a video or two that causes this error message for you?

Could you also check YouTube's HTML5 support page to see whether you have at least 5 blue boxes: https://www.youtube.com/html5

Thanks for your reply.

This is a link that gave the same error just now:

http://dailycaller.com/2016/12/29/scott-brown-started-his-on-air-fire-bombing-of-john-kerry-saying-with-all-due-respect-so-its-alllll-goooood-video/

On the HTML support page I have 4 blue boxes and 2 red (H.264 and Web VP8).

I appreciate your help.

I use a script blocker, but if I allow brightcove.com, brightcove.net, and llnwd.net then the video plays.

Possibly your problem is lack of H.264 support. Could you check here:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste mp4 and pause while the list is filtered

(3) If the media.mp4.enabled preference is bolded and "user set" to false, double-click it to restore the default value of true

Hi, I use adblocker+ and did not see brightcove.com, brightcove.net or linwd.net listed in the "blockables." Not sure if I was looking in th right place. Could not find another more appropriate place to look. Media.mp4.enabled was already set to default. Thanks!

Hmm, can you play the H.264/MP4 video on the following test page? Scroll down past the green/red table, that's old information which hasn't been updated and isn't diagnostic of your browser:

http://www.quirksmode.org/html5/tests/video.html

I can play all 3.

Try to create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Creating a new profile did the trick. As I add extensions and add-ons, I will test after each one. Thanks so much for your help!