Moving Trigger not detecting stationary MeshCollider

I'm trying to allow a user to select multiple objects by dragging out a selection region with the mouse. The objects are either cubes (using a box collider) or more complex shapes (using a mesh collider). To do this, I'm manipulating a box collider with IsTrigger set to true, which has a RigidBody attached.

The problem I'm having is that the selection box works perfectly for box colliders, but refuses to detect mesh colliders at all.

Things I've tried:

• Switching to a non-trigger collider and using OnCollisionEnter

• Calling RigidBody.WakeUp() on the selection box every frame

• Adding rigidbodies to the mesh colliders, and calling RigidBody.WakeUp() on them every frame

• Calling rigidbody.AddForce(Vector3.zero) on the selection box every frame

• Making the mesh colliders convex

• Changing the rigidbody velocity of the selection box

The only way I can get the mesh to interact with the selection box is if the mesh is actually moving with a rigidbody attached. Obviously I'd rather not have hundreds of static colliders turned into moving colliders with rigidbodies just so I can select them. Any suggestions?

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A couple of pics of my setup:

The selection box:

A cube:

A non-cube:

And my physics setup:

In the SelectionPlane, here's the code that repositions the collider:

         transform.position = startPos + (currentPos - startPos) / 2f;
         transform.Translate(Vector3.up * 1.1f);
         transform.localScale = new Vector3(Mathf.Abs(currentPos.x - startPos.x) * ScaleMultiplier, 1f, Mathf.Abs(currentPos.z - startPos.z) * ScaleMultiplier); ;
 

This is all using Unity 4.6.2f1