Movie Rental Problem with iTunes "Not Responding" and Not Playing

*The Situation*

I have been renting movies off of ITunes for over 2 years now and recently have had problems with movie rentals not playing on my computer at all. Let me preface by saying that I can transfer the movie to my iPod and it plays just fine. However, I would like to watch it on a larger, high-resolution screen. Also, I can play items that were purchased such as TV shows and music, but not movie rentals.

*The Problem*

So, after I download the movie rental and confirm that I want to start watching it and press play iTunes will play one frame with sound and stop all together and not respond, which results in me having to force quit iTunes and restart the application. This does not resolve the problem.

*Troubleshooting attempts:*

1. I have the latest version of iTunes (9.0.3.15) and Quicktime (7.6.5).

2. I have disabled DirectX in Quicktime.

3. I have reinstalled iTunes and Quicktime.

4. I checked my network connection for iTunes authorization.

I have contacted iTunes twice and they gave me my money back, but they didn't give me a reason or an explanation as to why this is happening. It seems like a fairly new development since I haven't had this problem in the past.

I do not have a gray screen problem like some of the other people are having. The movie just isn't playing and it eventually locks up iTunes all together.

Has anyone else had this problem? Has anyone been able to fix it?

Thanks!