I already asked for importing into a new library, Frank, but that was probably lost in my long list 😁
I am not sure yet by the symptoms, if it is a problem of this particular library, user preferences, or a weird kind of permissions issue.
It is good to see you and Kirby here. I noticed, that all three of my Mavericks Macs are showing similar problems with Aperture 3.5, but Harri is using Aperture 3.4 and I have no longer any way to test with that version. Kirby, are you still running Aperture 3.4.5?
On my macs, with Aperture 3.5.1, generally, after adding files to a folder, will it take a long time for Aperture to notice that the files have been added, and it will require to close the Import window and to open it again.
But Aperture 3.5 will show the files eventually, only it is annoyingly slow.
I have only come about one case, where Aperture could not access files in the Import panel, that the original poster could clearly see in the Finder, and that was due to file vault being enabled for the Home folder. And Aperture could neither access the Desktop nor the Pictures folder, nor the referenced originals.