QT 10 will play full screen if I double click an MPEG-4 file - no problems there. iTunes will also play full screen if I set the play window inside the iTunes frame then click on View/Full Screen. Odd behaviour indeed.
I have been in a couple of Apple Discussion Groups and some have this problem and some don't. The thick plottens!
My advice to friends is to hold off on Snow Leopard for a few more months. Strange stuff happens with iLife as well - I discussed a problem earlier on with some others on this forum.
Thanks.