Bethesda has just announced that they are taking ‘The Pitt’ off the Xbox Live service until further notice.
The English version of the file is said to somehow have been corrupted, you can find the full statement below.
We are continuing to look into the issues people are experiencing with The Pitt for Xbox 360. As of now it looks like the file for the English version on Xbox Live was somehow corrupted. We are currently working with Microsoft to remove the existing file off of Live to prevent any further downloads. Our plan is to replace it with a new file as soon as possible. We hope to have another update for you shortly.