Correct - for 64-bit guests, you must use the LSILogic SCSI adapter.
One question - if you already have a VM, why are you using converter to create a copy, instead of just using your host's filesystem commands?
I had the same problem, I finally fixed it by opening the .vmx file of the original to see what how they differed, it turns out that if you change the line scsi0.virtualDev = "buslogic" to scsi0.virtualDev = "lsilogic1068" in the new virtual machine's .vmx file it will work 😃
There are official work around instructions here: but I couldn't get it to quite work so I used the fix above