I will link to a youtube video showing what should happen.  I have linked to the specific part of the video.

it doesn't happen to me.  The elevator just doesn't open.

http://www.youtube.com/watch?v=FyW774tRwH4#t=8m30s

I don't know what point of the game it was supposed to be, but a few copies went out bugged that there was one point where something that was supposed to happen just wouldn't. If that's the case, you need to call Nintendo and they'll replace the game, though it'll take a bit

I think that's the gamebreaking bug many people were talking about.

This one ?: http://www.joystiq.com/2010/09/18/game-breaking-bug-found-in-metroid-other-m/

No...it's not a known bug. I dunno, I'd reccomend collecting some stuff and trying again

But is the OT's different from the bug Barozi mentioned (which is the bug i remember hearing about)

Metroid: Other Bug?

it's not the same bug.  there is no lava pit.

hmm. try collecting some more sutff?

No biggie.  The game's really not worth finishing.