wierd results in node-based materials for glass..

Hi everyone…
I was just experimenting with transparent shadows and node-based materials and came up with a few weird results…

The render while using nodes:


The render (same material settings) without using nodes:


Now i am confused as to what caused this black color to appear on the left side of the glass :eek:
And another problem, the plane receives transparent shadows for procedural materials but doesnt do so for node-based ones. Is there a work-around for this?? Or do i have to use “fake” transparent shadows by using spotlights etc??

Here is the node-setup i used:


Please help me out as i am not very familier with the node system of blender 3d and have just begun to understand it.

And here are the settings I used for transparency: