The people running Apple iTunes are more pro-active about taking care of their service then I first thought:

"Dear NAMEHERE,

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.