If you use extensions (Tools > Add-ons > Extensions) like Adblock Plus or NoScript or Flash Block that can block content then make sure that such extensions aren't blocking content.

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

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode

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

You can check for problems caused by recent Flash updates and try these:

• disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
• disable protected mode in Flash 11.3 and later
• disable hardware acceleration in the Flash plugin
• downgrade the Flash player to version 10.3 or 11.2

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

tried to do as you said--no change :-(

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

You can try to reset Firefox if you can't fix your current profile.

• https://support.mozilla.org/kb/reset-firefox-easily-fix-most-problems

If you reset Firefox then a new profile is created and some of your data (bookmarks, passwords, cookies, form data) is automatically imported and your current profile will be moved to the desktop (Old Firefox Data).

You can recover more data from the old profile (be cautious with doing that).

thank you so much for your help--I cleared cache and removed cookies. Still no video :-(

I can try to reset Firefox but I am SCARED. I have 100 very important bookmarks. Are you sure they will be imported???? Will my Firefox look exactly the same with the same "bookmarks"--they are very important for my job.

I am so scared to reset Firefox. Do you really think it will help? Are there any negatives that could happen? I am not very computer-literate.

Thank you so much......Melanie

You can export the bookmarks to an HTML file to have a backup.

• Bookmarks > Show All Bookmarks > Import & Backup > Export Bookmarks to HTML

You should always backup important personal data at regular intervals to prevent dataloss.

• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox
• https://support.mozilla.org/kb/Backing+up+your+information

You can also use the Profile Manager to create a new profile as a test to check if your current profile is causing the problems.
Then you can still revert to your current profile in case that is doesn't help.

• http://kb.mozillazine.org/Profile_Manager
• https://support.mozilla.org/kb/Managing+profiles

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

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If the new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

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

You can also try to reset Firefox:

• https://support.mozilla.org/kb/Basic+Troubleshooting

SOLVED, thanks everyone for your help.....