I have a theory to the problem -- ITs with the song Within You Without You. It appears to be corrupted the way it was uploaded.
Last night, all my songs worked except that song. After redownloading that song, BAM, Abbey Road is broken again.
An acknowledgement from HMX about this issue sometime later today when they get into the office would be great, but, further testing may be needed to see if its specifically that song causing the issue. All my DLC worked perfect until I installed that song this morning, though (on a 3rd re-download, even!)