I’ve successfully modelled a table with a glass top. The glass material came from:
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Every_Material_Known_to_Man/Glass
It works pretty well, except that the structure under the glass tabletop doesn’t cast shadows. The glass itself does cast a shadow. The table is sitting on a plane with a very basic brownish material. There’s a hemi lamp and a spot.
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If I understand what you’ve said, basically the ray casting shadows aren’t making it through the glass. Try turning up your ray depth on the glass transparency. As a debugger, move the glass to another layer and render. Shadows? Possibly your ground plane is set to not receive shadows?.
On the table try turning on TraShadow in the material buttons, Shaders panel. That allows for receiving of transparent shadows.
Like dschnell289 said, I’m not entirely clear on the problem. Maybe post a picture of what is going on.
-Laurifer