Many thanks. FIXED ! SUCCESS
Extended snipe hunt worked!
I had FIXED PERMISSIONS. No go.
I then did check Secuirty Plugins Enabled (they were)
Extensions DIX HiQ was enabled, turned that off. STill no go.
DId variety of things, SAFE BOOT, cleaned caches via Cocktail System, User & Internet caches, PRAM reset and even SMC reset. None seemed to work.
On Apple.com main page, tried several iPad videos, all failed same way, audio but blank video spinning spokes and QT controls showing but not working, NO VIDEO. Most CURIOUS, the Apple Special Event for Mar 2 (intro of iPad2) did play fine, audio & video. No other videos worked though.
FINALLY carefully checked Extensions and there was another Divx extension, Divx Plus Web player for HTML5, which was also enabled. DISABLED that, and SUCCESS!
Something weird with DIvx components. I had long ago tried some Divx players, deleted them, but I suppose some artifacts, components still there on my system.
THANKS for the hints. After a snipe hunt they worked.