This may not help, but I went through this issue awhile back, and found this post, and instantly I had both of those DLC's
Here is the post I found
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Disclamer: This is for Win7 users (and I would assume Win8, though I don't know about that) only!
It looks like no one's addressed this, so if it has been, I apologise.
Okay... just to start things off real simply... IF YOU HAVE ORIGIN, YOU DO NOT NEED TO DOWNLOAD ANY DLC! PERIOD!!!
Heh, sorry for the shouting, but I dare say I have your attention. If you bought or registered your Steam version on Origin then all the DLC should already be bundled in with the game. All you need to do is go to [C:\Program Files (x86)\Origin Games\Mass Effect\Binaries] and edit [MassEffect]'s compatability settings to [Win. XP SP2]. Run the game, and check your DLC. Both [Pinnicle Station] and [BDtS] should show up. Additionally, I'm running the game as the Administrator, so if it doesn't show up with the previous step, then do that as well.
Cheers!
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This post got both of the DLC's working for me instantly. PC version, I can not say for others
<<<EDIT>>> Also I don't play on my Xbox anymore, but I remember something about having a real problem installing both [Pinnicle Station] and [ Bring down the sky ]
I forget what the problem was, but I do remember it was a real pain to get them both installed at the same time. seems like had to do a complete un install, and re install, and install them in a certain order. It has been way to long, but I bet a google would find the problem.