I have a rather extensive theory, that I'm not so sure about anymore, which if you want to read it is here:
http://reachtheory.blogspot.com/2010/09/ai-theory.htmlIt has more to do with Halsey's Journal, but the gist as well as major supporting fact of the theory has to do with Dr. Sorvad's coincidental death. Dr. Sorvad is the dead scientist in this level, and the relay hub in Visegrad went dead two days beforehand right when Dr. Sorvad sent Halsey a message saying he was about to send her the 'latchkey'.
The basic premise of my theory is that the AI's in the data pads are behind what happened to Dr. Sorvad and therefore possibly bringing the Covenant to Reach
I won't go too much into my theory, but here's a discovery: In Halsey's Journal, it says that Dr. Sorvad was paranoid about his safety and that of his crew. The journal references a 'Farragut Station' and how people there had disappeared (farragut station is the old run-down building outside of Sword Base) in connection with what seems to be xenoarchealogical work. We know from "the Package" what Sword Base is all about in that respect.
In the journal, it says that Dr. Sorvad intentionally keeps a "skeleton crew", because he doesn't want too many to be sacrificed in case they 'find out too much' (that's the clear implication). The Data Pads make it clear that the AIs knew about the Forerunner for some time and did NOT want the humans to know about them. Read my theory for more evidence.
Interestingly, in "Winter Contingency", the label that appears in-game right before you discover Dr. Sorvad's body is "Skeleton Crew". At the relay switch at the end of the level, the dead civilians have a screwdriver, a voltimeter for EE work. Can we find out more? Maybe piece together clues about what really happened between the time Dr. Sorvad sets out for the relay hub to send the latchkey to Halsey, and two days later when Noble arrives and finds the Covenant there. It doesn't seem likely that the Covenant have been there for too long, Sorvad's daughter is still alive....
Also, a last bit of evidence. The radio chatter on overlook talks about how the innies might have hit the relay hub because it connects Northern Reach to the rest of the colonies (not the whole planet). The transcript I read mentions ?oilfields?, but I think this could be "ONI bases". ONI seems to like to build on top of Forerunnersites, so, is there a deeper connection between this attack, the latchkey, and ONI?
I'm saying this in this thread because I think search parties should keep this in mind as they try to find clues in the game about what was going on.