Not shadow behind glass

[DANIELE_CASAROLA]

Hi!
Please take a look to this shoot:

http://www.ossosso.com/scambio/Capture.JPG

It is a balcony. The glass on the front is clear, not glossiness, in fact the plant behind and the wall, all is seen clear as it should, only the shadow on the left isn't seen... and it make the glass seems like if it is satin.

What could be the problem? "Affect Shadow" for Refraction is enable on the material.

Thank you!

Ps
During Light Cache preview all is correct...

[tashko.zashev]

Hi,

Would it be possible to attach the scene file or part of it to see the setup ?
Which V-Ray build is this?