I downloaded a tv episode and it will only play the first 30 seconds even though it shows all has been downloaded.

Restart your Mac and try again.

I have exactly the same issue. I'm visiting in the USA but live in UK. If this is the problem then iTunes should not have let me buy it. I can't get it in BBC iplayer as that recognises I am abroad. VERY ANNOYING. It keeps going through the entire download but then plays 30 seconds. It's robbery.

I have had this problem for entire seasons of TV Shows with no solution. I get 30 seconds for what is supposed to be a half hour program and everytime I watch it download the entire thing. I WANT MY MONEY BACK, THIS IS AN ONGOING ISSUE WITH NO RESOLUTION.