There's posting on the Phase One Forum acknowledging this issue.
fwiw, I've found that I can import images from a camera when the camera is connected via USB and set to mass transfer rather than PTP. Not all cameras allow you the choice though. This doesn't always work but I've found that everything else fails all of the time.
I was too hasty to upgrade to Lion. I'd got used to Apple software working well when released. May be time now to be more careful/cautious.