I altered a vanilla bottle mesh, then followed http://cs.elderscrolls.com/constwiki/index.php/Blender/Custom_Collision tutorial and redid the collision. Yet, in game, http://img340.imageshack.us/img340/1305/bottles.jpg happens.

I must have tried a dozen different things, but this happens every time, no matter what. It's probably something really simple, but I just can't figure it out. Any help would be greatly appreciated.

In Blender, before exporting, be sure to apply scale and rotation (CTRL+A).
In NifSkope turn on the "Draw Havok" in Render menu and check if havok mesh is OK. If not, then check the Translation and Rotation in bhkCollisionObject: bhkRigidBody.

I did that, and the collision looks fine in NifSkope, but the problem persists, unfortunately.

Is there anything else I could be doing wrong? (Well, obviously. )

This hasn't actually ever happened to me, so take this for what it's worth, but I'm given to understand that things like this can happen if some of your collision normals are flipped the wrong way. In theory you can flip the bogus ones and it should work right.

Care to PM me a download link? I could take a look at it.

Yes, please! :laugh:

I'm still pretty new to Blender/NifSkope. If you could tell me what I'm doing wrong, that'd be great.

PM-ed you a download link with a picture detailing what I did.

lol, edoc to th rescue again, you the man!