think is codec problem but not sure how to fix as need the codec (1 Viewer)

[mbu10]

well most of the time runs fine and plays everything
but every 5-10 vids i play but only black screen with sound no video
if i stop and play again is genrally fine
think this has been happening since i installed coded for HD stuff ie makstora
reinstalled fdd over the top but still donig it
any ideas
thanks