After leaving the latest Mass Effect 2 DLC aside for a few days (I ran into a glitch), I went back to it and the glitch didn't pop back up. Maybe I just needed a clean restart of the game. It was worth it; "Lair of the Shadow Broker" is a pretty nice little piece of DLC, and it's interesting how seamlessly it adds into the game.
The contrast between how DLC works in ME2 and in Dragon Age is kind of interesting, actually. Both are BioWare games, but they behave very differently in this realm. With ME2, the DLC drops into your existing game (like the early DLC for Dragon Age did, so it's clear that it's not a technical limitation). The latest DLC for Dragon Age requires you to import an existing character (or create a new high level one).
This wouldn't be a problem except for one issue (at least on the XBox) - there's a character save limit, so if you've played a few times, you need to blow away (or archive off to a USB drive) older characters.
Why? Saves are just big disk files; there just doesn't seem to be a good reason for this. If you enjoy DAO, you've probably invested serious time into your characters, and blowing them away is painful. Maybe ME2 has the same issue, but since the DLC hasn't forced me into imports, I haven't run into it. I really hope they deal with this for Dragon Age 2....