Information from Play.com:
We are writing in regards to an order that you placed with us recently for Star Trek: The Next Generation - Season 1 Box Set (6 Discs)
We have just been informed by Paramount that during the manufacturing process of this item a fault with the sound on some discs has been discovered. Paramount are currently producing replacement discs that we will then be able to send out to you. A replacement copy of this item will be sent to you as soon as the new stock is received in our warehouse. Due to the nature of this issue please allow 28 days for the replacement to arrive. Once the replacement item arrives please dispose of the faulty item, there is no need on this occasion for the faulty item to be returned to us.
We are sorry for any inconvenience caused in this matter and we would like to thank you for shopping with Play.com.