VMware Guest Performance with x64 host

Been running into a confusing problem with slow performance under VMware Workstation 6.5.0 with a Vista x64 host on my new laptop.

I keep thinking it has something to do with PAE and 32 bit guests, but I haven't been able to pin it down. Messing with the boot.ini to disable PAE seems to help sometimes, but I think it is the placebo effect. No information found despite extensive searching in Google and on the vmware forums.