animation slowdown
 

Dear all,

I am experiencing a weird performance reduction (using an ATI Radeon 9700 graphics card) over the course of a ~20min animation (viewpoint movement gradually becomes slower and slower). It is not related to the frame rate which remains constant at 60 Hz, and I haven't seen it when I ran it on another PC with an nVidia card. Could that be related to some settings of the graphics card? Or any dubious Windows settings? Any hint would be greatly appreciated!