iTunes not playing purchased tv shows

I purchased television shows (standard definition) through iTunes and played them successfully on my iMac until I decided to watch one episode on my iPhone. Now, I can only watch the shows on my iPhone. If I try to play them on my iMac, I get the iTunes black screen of death (iTunes says it is playing the show, but all I see is a static black window) with "application not responding."

I tried the steps outlined here: http://support.apple.com/kb/TS1277 (iTunes: Missing Shared folder or incorrect permissions may prevent authorization) --

Mac OS X

1. Log in to your computer using an administrator account.
2. In the Finder, choose Go to Folder from the Go menu.
3. Type: "/Users" (without quotes) and click Go.

If the Shared folder exists

1. Open Terminal (found in /Applications/Utilities).

   Warning: This step involves modifying permission settings by entering commands in the Terminal application. Users unfamiliar with Terminal and UNIX-like environments should proceed with caution. The entry of incorrect commands may result in data loss or unusable system software. Improper alteration of permissions can result in reduced system security or exposure of private data. This option requires a non-blank admin password.

2. Depending on which version of Mac OS X you have, this step will vary. When entering the command, make sure to use a capital R:
   • On Mac OS X v10.5.8 and earlier, type: sudo chmod -R 777 /Users/Shared
   • On Mac OS X v10.6 or later, type: sudo chmod -R 1777 /Users/Shared
3. Press Return.
4. Quit Terminal.

That did not work. I have also deauthorized and reauthorized my iMac in iTunes and used the Disk Utilities to verify and repair disk permissions.

Can anyone help me resolve this?

Thank you!

I am using:

Mac OSX 10.7.5

iTunes: 11.0.1 (12)

iPhone iOS 6.1

(all are up to date)