Tried to hook up a pocket wizard to the pc terminal on the Canon 1DS MarkIII as well but with same result. Is there a conflict when using a flash mounted to the hot shoe at the same time as using a pocket wizard to trigger the profoto's?
Are the Profotos firing at all? If they are, it may be that, with the 580 connected, the camera is firing its preflash for TTL metering, which is the sync that is triggering the Profotos early. Have you tried the 580 in manual mode?
There should not be a conflict with the Canon 1-series cameras. I often shoot with a Pocket Wizard hooked to the sync terminal and a flash in the hot shoe. (There have been issues with the xxD cameras not allowing this in the past. Not sure about current models.)Will the Profoto fire at all, even without the 580 in the shoe?