This issue was noted as resolved in the latest 3.4.5 release.
Aperture 3.4.5 Update
- Addresses an issue that could cause Aperture to quit unexpectedly when deleting items from a camera or memory card after import.
- Memory cards are now ejected correctly when using the Delete Items option after import.
- Includes stability improvements
But longjohn123 says:
This was supposedly fixed on the last software update I thought but still having issues with it today.
I assumed, he has already updated.
if you still are having problems after the update to 3.4.5, the problem might be caused by a faulty card or a broken filesystem on your card.
Do you have the same problem with different memory cards? If not, reformat your card in the camera, or try a different card reader, if the problem persists.