Dafydd,
Thank you for your help, and I apologise for not replying immediately I have done some further checking here. We have Director Suite Version 12 on another computer. I have checked that version and the library videos play in Standard 2D Preview.
My video in Version 13 on this laptop now plays in 3D Ready HDTV (checkboard). The colour looks correct and the sound is perfect.
Is it possible that I have checked or unchecked a box in Preferences? I have compared the two lots of Preferences and they look the same.
Is it ok if I just use the 3D Ready HDTV (checkboard) or will this cause problems when I come to render the video?
Thank you.