Can you confirm that this is with movies you had no problem with before, or only with movies you have downloaded recently?
Yes it was with movies that were fine previously, i have re-installed the firmware plugged other usb sticks/hdd in and the problem seems to be sorted. However my main 2tb external hdd files are still unwatchable but i have discovered that the caddy it is in is dodgy. Before installing the firmware again all drives i plugged in would not play correctly but now they are fine.
Very strange problems but hopefully sorted.
Thanks to all members for there input.