Hi,
I seem to be experiencing the exact same problem. Animating the Radius of the Defocus effect (other parameters left to default) leads to ugly stepping, using 8 bit as well as 32 bit pixel format. This doesn’t happen in Vegas Pro 9. Here is a comparison, rendered losslessly using CPU only.
Any idea what might be causing this?
David
https://youtube.com/watch?v=gy1WV4RcuX0