2009 octad with loads of RAM and SSD to store the VM file.
I tried the VM with standard settings (1 core, 1GB RAM), as well as my own settings (4 cores, 4GB RAM) and tried it on a mechanical drive as well.
The image file is fine, I guess, since the VM boots without problems.
What Fusion version are you guys running? I'm on 3.0.0.
Another option would be to Bootcamp Lion, unfortunately BootCamp doesn't work on external eSATA drives and neither Parallels, nor VMWare recognise partitions that haven't be created via BC. Pity.
i think 3.0.0 might actually be your problem. because i do recall that a number of hacks required the light version of 3.1.1 (for some particular reason) in order to get osx running. its a free download if you are a registered vmware user, so maybe that is worth a download?