Physics 2.5 64 bit: Object falls through invisible "hole"?

I’ll start off by saying I’m pretty new to Blender, so there may be something obvious I just don’t know to look for. I did search several topics/Google trying to find an answer though, with no success. The model was created in Sketchup, Converted to OBJ via MeshLab, and Cleaned up in Blender by removing some edges created by Meshlab, “remove doubles” (each face/edge were not connected after import), weld verticies, and convert tris to quads.

Problem: I have a jar modeled and several marbles. I’d like to use Blender’s physics engine to drop the marbles into the jar in order to create a tightly packed random arrangement, just like they would appear in real life. The problem is that when I start the game engine, the test marbles drop to the bottom of the jar just fine; they then roll around a bit and then drop through some invisible hole at the bottom of the jar. I can’t find anything wrong (normals pointing the wrong way, etc…) with the model in that area that I can see - though I could be wrong.

What I’ve done in Blender Game: Jar: Static, Actor, Collision bounds (triangle mesh) with 0.1 set in the margin. Marble: Dynamic, Actor, Collision bounds (sphere) with 0.1 margin.

Using Blender 2.53.0 Beta 64 bit in Win7.