Are sheets broken in Leopard or I am doing something very wrong?

FROM : Toplica Tanaskovi?
DATE : Sun Jan 13 00:08:21 2008

I am trying to display custom sheet upon displaying new window in 
Cocoa document based app.
The problem is that sheet is not displayed as sheet but as normal 
standalone window!? As far as I remember
the method I'm using worked perfectly in Tiger. What am I doing wrong?

   Please find ripped code at: http://galeb.etf.bg.ac.yu/~toptan/iPGWizard.zip

Thanks.

Toplica