Okay, I just got it to work after going through this thread, figured I'd let everyone know what I did and not be lazy and just be on my own merry way.
So, I'm on Windows 7 64bit.
I already owned (and registered) a retail copy of DAO (had also registered the DLC that enables Shale as a companion.. love that guy)
I wanted to play Awakening, and when the steam sale came up with the Ultimate eddition, I figured, well, its cheaper then just Awakening on its own, AND has all the DLC.
I downloaded through steam, installed, logged in, DLC there, but not enabled. So I basically did everything, exept for the file deletion.
Quit DAU.
Go to the Bioware page where you put in your promo codes.
Add the promo code from steam.
Logged out/in and checked to be sure [a little paranoid? sure, but I wanted this to work]
Went into the steamapps/redist folder, ran the exec. went back into DAU.... nothing.
Back to the Bioware account page, only this time, Also registered the DAU code in the registered games section.
Back to the redist folder, ran BOTH execs.
Launch back into DAU. New game still gives warning.
Open the DLC manager within. Still showed as disabled.
Manually logged out of my account within DAU. And logged back in, without quitting, still on the Downloadable Content - Installed Content tab.
Game appeared to lock up for less then a minute [though the music still ran] screen refreshed, and all content was enabled.
Thanks to everyone who suggested any of the solutions I eneded up using. Hopefully others will get theirs to work with my combination. GLHF.