I'm using Vista Ultimate 32 bits and Poser 7 (tried without updates and with SR-1 and SR-2). 

I had the same freezes (render reaches end then blocks half the time, I had to terminate Poser and restart again) until a few days ago when I udpated my NVidia graphic drivers.

Since then not one freeze ! All my renders work perfectly now. /me crosses fingers

I haven't tried animations yet though.

Yours friendly

Lunedust