Unfortunately iTunes 11 has broken some of the nice automation scripting in the current version of Seas0nPass.
An updated version of Seas0nPass is in the works, but for now a workaround for using Seas0nPass with the new version of iTunes can be found below.
- Run Seas0nPass normally through where the script error occurs.
- Locate the newly created IPSW file (named AppleTV2,1_5.0.2_9B830_SP_Restore.ipsw) On a Mac this will be located in the ~/Library/Application Support/Seas0nPass folder. On a PC it can be found in the /Libraries/Documents/Seas0nPass folder.
- Open iTunes, and select the Apple TV in the lefthand sidebar.
- Manually select the firmware file that was created by Seas0nPass. This is done by holding Option and clicking the Restore button (Mac) or holding Shift and clicking the Restore button (PC).
Update 12/18: Seas0nPass 0.8.8 is now available which restores automated scripting in iTunes 11. http://support.firecore.com/entries/387605