Hi Gen, Hi Stwert.....

Thanks both for your replies.

Gen, yes the frame rates have been matching up.

Stwert, yes.... I think you have hit the nail on the head....
I've just been round my friends rendering out one of our animations, and he's a little more tech savvy than I am and it would seem it is probably just my media player/s and/or CPU having trouble just playing the vids as they are very large file sizes. His computer is much newer and faster than mine, and his rig handles them fine. I'm overdue an upgrade on my hardware.

Eg the last video I rendered out of afx was just short of 800 mb.
And I've rendered out larger also recently.
It's crazy.... We rendered out a video from afx, 33 seconds long, and it was 2.1 gig.
We put it in premiere and exported straight out as h264, and the same video was 50mb, no drop in quality.