Just a long shot (and I haven't read through the whole thread to see if this hasn't already been discussed) but I've noticed that a few hours into the game (not to spoiler, I've just done the photographing the 3 "things" bit), either the game is playing up or my 360, or both.
The symptoms are that the game seems to pause frequently and randomly, almost as if its loading something...each pause happens for a second or two, much like an high-end PC game struggling on a low-spec PC - it didn't seem to have been happening earlier in the game but plaguing it now. I've tried taking the disc out (no scratches) and rebooting but it's still happening.
It did download an "update" recently and I wonder whether that's caused it? Or perhaps it's the level I'm on puts some particular stress on the graphics/game engine??
My main worry is that its my 360 beginning to go west - it is an "original" model and other friends who got them at the same time have all had total failures, so I guess this could be my machine's time?
Anyone else get these wierd hang-ups in Bioshock?
edit: well, I guess I should have searched google BEFORE posting this
It's a HDD/cache thing apparently:
http://forums.2kgames.com/forums/showthread.php?t=9247
edit2: reading the last few posts of that 2k games thread it turns out that it sounds more like the update has caused this - people are clearing their 360 cache (and NOT re-updating the game) to get rid of the issue. This IS the internet mind, so who knows what I should believe. Sigh.