strange behavior with normalized view port rect

Hi!

I use a camera to draw a little top-down view in the upper right corner of my game. For this I use the Normalized View Port Rect with the sizes 0.7,0.6,0.3,0.4. The camera itself is orthographic. When I use this on the machine where I work (macbook pro) everything is fine. Moving to another machine (over the webplayer), I get a strange behavior:
The rect in the upper right displays everything but terrain details (trees, etc.). The terrain details are rendered instead on the bottom right, giving an ugly glitch. The screens of the other computers have different sizes and aspect ratios. Could this be a reason? But I really wouldn't know how to set a normalized view port rect to an aspect ratio...

Thanks
Gabriel