Hi gordonmacwilliam,

try to Turn off hardware acceleration in Firefox and "disable the hardware acceleration" in the Flash Player too :

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

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

thank you

The hardware acceleration was not the problem. However, disabling the Adblock Plus 2.1.2 extension as suggested in the rest of the troubleshooting guide to which you directed me did solve the problem. Disabling the Adbloc fits the symptoms since YouTube videos do not start with ads, whereas all AOL videos do. The Adblock extension stopped the AOL ads from playing which in turn prevented the AOL videos from appearing. Thanks for your help!

you are welcome