error 12001?

HI I have tried downloading a rented film with iTunes, this error 12001 appears but is not listed anywhere in the troubleshooting info - the film can be viewed correctly for 50 mins then stops. The download of the file seems the right size for the whole film, but it stops halfway. Any suggestions... Tell the truth, I had such trouble signing up and so forth, I think downloading a legit file is MUCH too much trouble, frankly... 3.euro 99 cents for what?