I can confirm (unfortunately) the problems described above, GFW Live Achievements "Ufo chrashing" and "Explode mid-air" do not unlock; running the game underWin7 Pro x64.
The importance of achievements is surely a matter of taste and might be considered non-critical, however I'd expect a patch to up, disregarding whos fault this was.
The game was sold with the LIVE feature, which is partly buggy, any of the involved parties should show some interest to patch that:
Microsoft - because they have include Dark Void into the LIVE portfolio, featuring a list of achievements with at least 2 of them non-achievable. Bad!
Capcom - because they are publishing the game, it should in their interest to supply their customers what was offered and paid for. Not working achivements leave some unhappy customers. Bad!
Airtight - because they were developing the game and probably know it best, certainly they wouldn't want to be known to develop only "almost" working games. Bad!
From my point of view the 3 parties should get into some decent discussion how to work this out, offering a patch soon.
Thanks and forgive my grumpy tone,