I seem to have answered my own question – my sequence setting for HDV was 25fps and I was trying to be clever (doh!) and export at 24fps frame rate in QT conversion setting. Seems to be alright now. Which is nice. I’ve closed my own loop. Hurray for that big ‘ol learning curve… just a bummer it’s always against the clock!
Thanks for your responses. It is, as David said, that I knocked the User bits button on the menu under the screen – and as, like him, I don’t set User Bits either, it was reading 00000000… Silly but really frustrating! Thanks for all your help.