Where are your Aperture/iPhoto Libraries located? On an external drive or your system drive? If external: Is the drive locally connected, or a network volume? How is it formatted?
Check the settings and preferences, that are shared by iPhoto and Aperture:
- Your login items: Do you launch any third-party application/utilities on login? Or have preference panes installed to be used with image capture? Do you have any Aperture plugins, that may no longer be compatible?
- The image capture preferences are shared between all photo apps: Try to remove them.
- The iLifeAssetManagement folder in your library is shared by iPhoto and Aperture.
To remove the image capture preferences:
- If Aperture is running, quit Aperture, and log off and on again.
- Open your user library from the Finder's Go menu: Hit Command Shift G (⌘⇧G) and then type in: ~/Library/Preferences/ then hit return.
- In the window that opens remove "com.apple.ImageCapture.plist"
- and look into the subfolder "ByHost": if there are files named com.apple.ImageCapture something .plist remove them too.
then try again.
If you are using PhotoStream, try to remove the iLifeAssetManagement folder from your User Library: (it is located in the Applications Support folder). This folder is also shared by Aperture and iPhoto in your User account.
Removing this folder will remove the local copy of your PhotoStreams howver; so make a backup, if you want to save the images.
Please report back with the results, if this does not help.