Linux bubastis 3.10.25-gentoo #10 SMP Thu Jan 30 22:17:35 UTC 2014 x86_64 Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz GenuineIntel GNU/Linux
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1100M] (rev a1) (prog-if 00 [VGA controller])
Broken: git 08bf531956b1c1cff3319d119e8aba55b7a09b9e
Short description of error
I might have discovered a defect in the Blender Internal raytrace logic.
When a ray travels through a translucent object, it will continue on to touch objects that are NOT in the current render layer.
If you have a translucent block in layer 1 and a monkey head in layer 3 the monkey head will be visible "through" the translucent block in the rendered image for a render layer that includes 1 but not layer 3.
This will eventually expire from pasteall, but until then it will save you the trouble of rendering the blend I'm about to attach: