Running virtual machines cannot be moved from host to host unless the processors on the host machine are very similar, e.g. you cannot move an guest from an AMD host to an Intel host without shutting down the machine.  However, if you shutdown the guest, then there are no such restrictions. [more]

I had a guest machine and it was shutdown. It would not move from and Intel host to another Intel host. The machine was a 64bit machine and I had remembered from the VMware conference that 64bit machines used the virtualization technology (VT) available on the more recent chips whereas they do not use it with 32bit hosts. VT is turned on and off with settings in BIOS.  I checked the BIOS settings on the two machines and sure enough, the VT was set on one machine and not the other.

Summary: An incongruous VT state will prohibit the movement of a 64 bit guest machine from one host to another … even in the shutdown state.