Fallout 3 Broken Steel DLC Now Available

Bethesda's third DLC pack for Fallout 3, Broken Steel, is now available on both Games For Windows Live and the Xbox Live Marketplace.
You may have dealt the Enclave a serious blow at Project Purity, but their forces are still out there, and still pose a grave threat to the people and security of the Capital Wasteland. In Broken Steel, you'll continue your current Fallout 3 character past the events of Project Purity, and work with the Brotherhood of Steel to eradicate the Enclave threat once and for all. You'll travel to new locations like the Olney Powerworks, wield destructive new weapons like the Tesla Cannon, fight powerful new creatures like the Super Mutant Overlord, marvel at the destructive power of Liberty Prime, earn new Perks like the devastating Nuclear Anomaly. and play Fallout 3 all the way to level 30!
Unfortunately, many people who have downloaded the 800-point add-on are reporting that it's unplayable:
I'm trying to download and install Broken Steel using the Windows Live Marketplace Client - the content downloads but then instantly fails to install giving the error message:

"Not a cryptographic message or the cryptographic message is not formatted correctly. (Exception from HRESULT: 0x8009200D)"

I'm updated to the 1.5 patch and have both of the other DLC packs. I also don't have any other mods installed or programs to deal with mod management etc. I do have the GECK installed but I can't see why that would cause a problem.
Word from Bethesda is that they're working on it:
Also Ill just say it here. We are looking into it. Sorry for the inconvenience for all the fans and playas out there.

Note I am even getting the same issue :\