Glass shader blocks light? I know a commonly duplicated question is "Why is light not passing through glass?" or "Why does my glass shader ignore lighting?", But mine's a bit different.

The Problem

I 3D modeled a type of weapon called a kukri in Blender, and I created a little display for it:

The speckles are the lighting emitted from the little spotlight-type things on the corners, I'm just running low samples at the moment.

As you can see, the shading looks dandy. Now let's see when happens when I put a glass cover on top of it:


Everything on the inside goes dark. Here's a representation of the geometry of the cover:
  

What I've Tried

I've tried the following node setups, neither of which solved the problem.



Here's my settings:



Download the .BLEND
Change clamp indirect to 0.  You have it set to .01, which feels like it should only affect it in a small way but in truth the smaller the value for clamp the more of an affect it will have.  0 = off.