The people running Apple iTunes are more pro-active about taking care of their service then I first thought:
Thank you for downloading "Sundown" from LOST, Season 6. The video you received may have had some noticeable audio quality issues.
To correct this problem, we placed a new copy of this item in your download queue. To begin downloading, click this link:
Check for Available Downloads
Or, you can open iTunes and select Check for Available Downloads from the Store menu."
I bought that episode months ago
Good luck with your scenario Kari.