Using Finder to Show Package Contents, then File | Find, "File visibility" = Invisible, I see many .AppleDouble folders.
I believe this is the root of the problem - any file which begins '.Apple'is a reserved name and so cannot be copied back to the NAS. I don't have a solution - am still looking. But you have confirmed that this scenario occurs with more applications than just iPhoto.
I'll post back if I figure any way forward - but maybe Netgear will come up with something
EDIT: One thought - as this is caused by AFP access to the NAS, maybe copying the packages back via CIFs will workaround the issue
EDIT2: From what I can see, this creation of .AppleDouble folders by some applications is a 'feature' of those applications so that networks shares can be supported. Other than to use an non-AFP protocol to copy back the packages, the only other documented 'solution' I can find is to delete these folders from the package - not something everyone will be comfortable with.
I've tried searching for a netatalk forum to post some questions, but there doesn't appear to be an active forum available. Also I'm having difficulty accessing the mailing lists advertised on the netatalk site.
I'd like to request that netgear investigate this and post recommendations of how to overcome the issue. It appears to be caused by applications not expecting to access network shares over AFP (I'm sure Mac OS X server deals with this somehow) conflicting with netatalk with both creating files with the same name. As such I don't think the netatalk team would consider this a bug, but there has to be a workaround where transfer over AFP is possible without havign to manually delete files in the original package.