hello, please see if updating your graphics driver is making a difference - this should be the right link for your model: http://support.amd.com/us/gpudownload/windows/Pages/radeonaiw_vista64.aspx

I updated the driver and restarted the computer. Unfortunately, it did not help- even I set "enable hardware acceleration" unchecked and cleared the cookies and caches. Please give further helps and tips. A zillion thanks.

when other browsers are not affected then maybe it's an issue with the protected mode in the flash plugin (which adobe has introduced for firefox only) - you could try if downgrading to flash 10.3 (which is still supported) or disabling protected mode makes a difference.

So, disabling the Flash protected mode makes the freeze/hang problem go away.

I guess if I want to continue using Firefox I have to leave protected mode disabled.

Of course, there's always Chrome . . .

I downgraded to Flash 10.3. The matter becomes worse: No video from Facebook Firefox; just the sound exists with a black screen. However, the videos from Facebook Chrome are still OKed.

attobuoy, in case you'd like to troubleshoot the issue further, it would be best to contact adobe's support & file a bug report at bugbase.adobe.com (choose "Adobe Flash Player" as the product & "Browser Integration" as the product area), since they will have a better understanding of the internals of flash protected mode & therefore may know what else might be at the root of the problem you are seeing and come up with a fix eventually.

Actually, when I restarted Firefox, the video came back- but it is still blurry.

Giui, i'd recommend a rest of the browser as a next troubleshooting step...

Refresh Firefox - reset add-ons and settings

Thank you, Madperson. You're so kind. I will be in touch with Adobe.

Take care, Sir.