I have exactly the same problem as Bulldog with my 505 and iMac, running SL. I have uninstalled, installed and reauthorised, or tried to. I have conferred with Sony and Waterstones while reading reams of online support pages. However the only thing that works for me is a Vista Dell laptop with my older version (2.5) of ADE. Until something changes, eg they bring out an update for the Mac, which doesn't require me to meddle in the programmes, I'm sticking with that Dell. It's a nuisance, but at least I don't try and launch my 505 or iMac.
Q? Is it feasible that the UK Sony programme to authorise the PC is also different to the US system?