Logging this on the interwebs to hopefully save others some headaches.
Installing FreeBSD 7.1 amd64 under VMware Server 2.0 (build 122956, 2008/10/29) on a Vista 32-bit host, and get "BTX Halted".
Solution is to enable Intel Virtualization in BIOS. However if your BIOS also has Intel VT-d (Direct I/O), do not enable this.