I've tried the html solutions... including the one referenced via the link you posted. No workie.
I can get text in the cell to center but not the actual flash flv video... it continues to left jusfify no matter what I do.
I've Googled and others have this problem... but I haven't been able to quite understand how to fix it.
I came to the conclusion that it was not an html issue but something to do with the way the video was created... or something... maybe in the java script that played the file.
Regardless, I need help solving this one !
I'm sure I'm missing something obvious.
Also look at the html tab in yout publish settings. Another thing to consider is if you're trying to get yout flv player centered on the stage and the registration point is top left then to place on the center of the stage your flvplayer.x is stage.stageWidth / 2 - your flvPlayer.width / 2 and y would be stage.stageHeight / 2 - yourFlvPlayer.height / 2