Why is Poser 7 so much slower than Poser 6 on my dual-core PC? I thought Poser 7 handles multiple cores better?

For example, using (Poser 6 Hi Res Jessi + bikini top + bikini bottom + strand hair) immediately after program start, with no other changes:

• Poser 6 render time: 2:30
• Poser 7 render time: 6:45

I have an AMD64 X2 4400+ with 2 GB RAM.

I would have thought that Poser 7 would have been at least as fast as Poser 6, if not faster.