Hi Klaus, Hi Graeme, many thanks for you support and your time looking into this. Meanwhile I had to go back to some "real (photographic) work" and wasn't able to pursue this issue any further. I guess I will file an Aperture bug report as soon as I find the time. For the moment, I've decided to postpone the upgrade to OS X Lion for my main workstation. Probably anyway a good idea to wait with that until Apple has shipped some bug fix upgrades for Lion. Thanks again. Andreas