[Ron]

Thanks for your help Rob.

Actually it turns out that it has something to do with the compression of the actual video footage used (which leads me to another question posted under another subject)

I have found that if I used footage which has been recompressed through the media manager, both viewer and canvas windows are playable in the monitor.

I have been using some test footage rendered from a Digital Juice set, and also tried rendering something out from After Effects, with the same effect.

So in effect, everything is working fine – I just have to find out the best codec to use when rendering QT files apparently.