Did you try to disable hardware acceleration in the Flash player (protected mode doesn't apply to XP)?

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

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

well, thanks for suggestions ... but problem persists.

When starting ff in safe mode, some times i have video and sometimes i don't.

It is just like starting ff in ordinary mode - sometimes there is a problem with video and sometimes not.

However, the video problem occurs more times than when it goes ok.

I unticked the hardware acceleration box but it made no difference.

Also I have played around with all the add -ons and (only 4) extensions ,disabling and enabling them, to no effect.

The odd thing is that this video problem is not always consistent - sometimes it occurs and sometimes it doesn't..

I have webroot anti-virus and it tells me that my laptop is clean.

There is no Video problem in chrome and IE.

.....A few times in the past, this problem occurred but things came right by themselves.

I have been a fan of ff for many years.

Did you try to disable hardware acceleration in the Flash player?

• http://helpx.adobe.com/flash-player/kb/video-playback-issues.html

Flash "Display settings" window:

• http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.