Hey Cage,

I know I am a little late to the party here, but I just recently experienced the same problem that you had and after going through the same headaches that you went through trying to figure out why it wasn't working, I finally found the problem (well at least for me and hopefully for you).

Apparantly there are certain video codecs that conflict with Poser 8. I had the K-Lite codec pack installed on my system and once uninstalled and an alternate codec pack specific for Window's Vista x64 installed in it's place the anti-aliasing in Poser 8's preview worked again.

Hope that helps you and anyone else who may undergo this trouble.

~Jack