It's a licensing issue with all DLC.
Anyone who had a system crash on them, and got it replaced by MS
should call up and start demanding replacement points to re-purchase
the content. IMPORTENT - You NEED a DIFFRENT gamertag to get the MS
points and to purchase the content for it to be licensed to the new
system.
Any other situation, you are unfortunately out of luck
until either it's fixed, or MS removes/enhances the DRM.
The DRM on the 360 works on 2 levels,
the original system serial number and the Gamertag; in that order.
Meaning, if anyone using the original system that the content was
downloaded on tried to access it, it's unlocked immediately because
the serial number matches up. If the serial number does not match up,
then the content checks Xbox Live to ensure the license is proper on
the gamertag. If game makers decide to be lazy, the problems listed
here happens. Or at least smiler problems happen. I downloaded
content at a friends place, and brought my HDD back to my place
knowing the restrictions. Well, even when connected to Live the game
wouldn't register the content. After about 5 months, I got MS points
refunded, and downloaded the content using a different gamertag, and
everything worked just fine.
We need a defragmentation and check disk utility! The NXE lag, it's gone. WOHOO!