FO3 content, Tenpenny Tower. I decided to let the ghouls swarm the place so that I could get the inventories of the merchants with minimal risk. However, once the ghouls are attacking, the inventories (including safes) are empty.
I reverted to a pre-invasion save, and sure enough, the inventories were there.
I googled this problem, and couldn't find anything on it.
Could be a mod issue, I suppose, though I can't recall any of the mods I've installed nerfed the game in this way.
I've not done this quest this way before, but I saw someone else do it, on an xbox, where he could get the shops' inventories during the attack.
Modlist:
http://pastebin.com/64NvHWCg