I guess this is a recent development with Facebook, which is failing to recognize the latest preview release of 64 bit flash “Square”. It fails to play any video, or upload and photos using the flash photo uploader. Keeps telling to upgrade to the latest version of the flash player.
To get around this problem, you will have to remove the latest 64-bit flash player and install the 32 bit flash player 10.2 which is available in the Ubuntu repositories. So, in short, an avid facebooker cannot use 64 bit flash in Linux. What a shame!