http://www.nikonchat.com/nikon-software-snow-leopard/

Image transfer for Mac Nikon D300 – problems?
I was fortunate to be invited to a nikon d3000 for my wonderful other half, a few months ago. We both have Mac (MacBook and MacBook Pro) with Snow Leopard. With all the other cameras I've used have not had trouble transferring images (even with other Nikon digital SLRs) – just plug in the USB, turn on the camera and zoom photos in iPhoto. However, for some strange reason, the D3000, just does not mount any of MacBook. I installed the nikon software that comes with the camera but it just freezes or tells me I have to download Rosetta, who proceeds to treat to download then hangs. I am totally confused and have never had this problem with a Mac before. I'm used to plugging things and make them work! Does anyone have any suggestions? I have many beautiful photos that I want to access!
Being a type of PC that I like to blame their problems on the fact that 95% of the planet is running on Windows, and that is how the cameras are configured – it is probably not true, but I like a PC. The easiest way to solve this problem, I think, is with a card reader. Your MAC should see a reader as a drive to everything you need to do is copy / paste. I have three digital cameras, three different styles of cards for so I have three readers … they all work this way and also gives me the flexibility to put my photos where I want to be instead of having the software to decide – I love it. All you have to do is plug your card into the reader, connect the combination in any available USB port and wala!