Kris, have sometimes same problem, its seems that its something with allocationof resources managed by windows, onthe same dataset im get all cores to work but sometimes only one....
Try restart PC, run JUST the PSCAN and nothing else and test on the dataset......
Im digging ontro that, but as im say its something with Winddows 7 64 bit and its resource allocation..
Or you get it on any dataset
For the aligment try this settings
Aligment : HIGH
Pair preselection: GENERIC
if proper shooted it should speedup the process up to 20x as have personaly tested
but depends of the scene, sometimes its work not good......
Let us know with results...