Aperture cannot access this library, aperture cannot access this library

Question

I received this message today when I tried to open the aperture 3. The library is on an external LaCie hard disk plugged into the imac

Answer 1

Andrew,
are you the owner of the files on your LaCie drive? If not, I'd try to reset the owner:
First check your current user id: Open a Terminal window:
Enter:
    echo $UID
On my system this will print : 502
Then check the UID associated with your La Cie files:
Enter into the Terminal window:
     ls -an
then add a "space", then drag the icon of your La Cie drive from the Finder to the Terminal, to enter the path to the drive, hit "return".
This should print listing similar to this: and the second column should correspond to your UID.
bash-3.2$ ls -an /Volumes/HermioneMedia
total 41240
drwxrwxr-x@ 45      502  20      1598  5 Aug 09:43 .
drwxrwxrwt@  5      0    80       170 11 Aug 16:09 ..
-rw-rw-r--   1      502  20      6148 11 Aug 14:04 .DS_Store
d--x--x--x   8      502  20       272 29 Jul 10:55 .DocumentRevisions-V100
drwx------   5      502  20       170  5 Mai 16:53 .Spotlight-V100
drwxrwxrwt@  5      502  20       170 28 Jul 15:31 .TemporaryItems
d-wx-wx-wt   3      502  20       102 11 Aug 16:09 .Trashes
If you see a different number, try to change the ownership:
Type:
sudo chown -R $UID
then again add a "space", then drag the icon of your La Cie drive from the Finder to the Terminal, to enter the path to the drive, hit "return". You will have to authorize as administrator, so double check what you typed. This will set the user id of all files on your drive to your own user id.
Regards
Léonie
PS: you may want to look in the Mountain Lion Forum as well, for example:
Permissions problem - unable to write to external drive
there seems to be a similar problem discussed, and I hope we will see answers there soon.