Bethesda has piped up about 
problems with the Broken Steel DLC for Fallout 3.
Of the PC error, which won't let some players install the add-on, SPOnG was told, "We're seeing the same error, which is a Games for Windows Live DRM Install error. Microsoft  is working on fixing it, and we'll let everyone know once we've verified it."
Problems have also cropped up with the Xbox 360 version of the DLC, with some players reporting that Achievements earned through the content are not appearing on their main Achievement list.
SPOnG was told by Bethesda that, "The Xbox Live servers don't seem to be fully synched yet with the additional achievements. This should fix itself automatically soon. People won't lose any achievements."
For more on 
Broken Steel, see 
SPOnG's preview and 
Q&A with Bethesda's marketing VP, Pete Hines.