Liquid-in-glass-problem

I was making a glass filled with liquid. But suddenly I got this http://kuvax.net/i/?4467lasol_total.jpg . The liquid is suppossed to be transparent

I have done glasses and liquids many time before but this is the first time I have something like this. I have tried to change all things in the scene but the result remains the same.

Heres render of the glass:
http://kuvax.net/i/?5864lasol_lasi.jpg

And here’s the liquid:
http://kuvax.net/i/?8026lasol_neste.jpg

Separately they look like as they should but no together. As we see the glass causes the black color of the liquid. But why? Even wothout shadows and mirror values the result is the same.

Here’s the .blend file:
http://www.badongo.com/file.php?file=lasol.blend__2005-12-10_lasol.blend

How can I get transparensy to the liquid in the glass?

Increase raydepth in Yafray tab.

Oh. Thanks.