Bethesda's DLC - the Pitt - for the highly acclaimed Fallout 3 launched on Windows and Xbox Live today and preceded to cause all sorts of problems on the latter.
The problems appear to relate to missing meshes from the DLC. At least according to a moderator on the official forum. Princess Stomper - a moderator - "Since yellow exclamation marks were an indicator of missing meshes in Morrowind and Oblivion, I would personally guess that the red exclamation marks denote missing meshes in Fallout 3.
"If that is indeed the case, you just need to wait for the missing files to be uploaded and it will resolve the problem fully and instantly: with Morrowind, a missing mesh or texture could cause a crash, and just adding that file would fix it. If that is the problem in this instance, then there is absolutely nothing that any of us can do (short of creating the missing art ourselves!) but wait for a fix."
A user called DevenTarn posts the following, "I've just finished speaking with a very helpful lady in Bethesda (yes, I called the US from the UK)...
"Confirmed... missing/corrupted texture files.
"Not known... total filesize (as shown on the marketplace), the lady was unable to access xbox live marketplace when she tried."
The Bethesda team is still working on the problem.