yeah check that you do not have laminar objects would be my guess.
Haha, I also remember learning mental ray. If going from 1 to 2 is good then going from 2 to 1024 should be UBER! Three weeks later when my render finished I went back to the default settings are fine! (smile)
I have watched countless tutorials and read the docs many times and the mental ray settings are still a mystery to me. Half the time, if you try to follow the documentation, the time you spend fine tuning the settings to get the best render takes 1000 times longer then the render it self.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675