Aperture library not seen by ilife or iTunes

How are you sharing the library between the two users? What changed on the system when it stopped working?

that I was exporting projects and creating additional libraries to reduce space on the hard drive.

Your Aperture user preferences may still be pointing to the last library you opened from your main account. iTunes reads the "com.apple.Aperture.plist" in the "preferences" folder in your user library to find the library to open. It may help to trash this file and to force Aperture to recreate it. But since you are using Mt. Lion I'd log off and on again after quitting Aperture and removing the preferences.

The library sits on the hard drive

Where exactly? A shared folder may not be enough, if the permissions inside the library do not allow iTunes to access the iTunes photo cache inside the library.

Regards

Léonie

The folder is shared and I apply the permissions against the shared folder to ensure both accounts have access.

Each time you write to your Aperture Library, the items inside the library you edit may change the ownership to the user that is editing the library and the permissions inside the library will change. The only safe way to share an Aperture library, so that two users can read and write is to have the library on a disk (external drive, separate disk partition, or writable disk image) that has the "Ignore Ownership" flag set. This is explained in this support article for iPhoto Libraries, but for Aperture libraries goes the same, see: iPhoto: Sharing libraries among multiple users

Hopefully Frank has some more ideas - I still do not see from your answer to his question what exactly changed, before it stopped working.

One more thing to check: Sometimes the iPod Photo Cache gets corrupted and then iTunes cannot open the library. Try to remove it from the library as described here: iTunes: Understanding the iPod Photo Cache folder

Deleting the cache should have no other consequences then that the next sync with iTunes may take longer.

So what exactly do you see when you are in the edia browser in the account that is not seeing the Aplerture library?

Are there no images at all, old images, images from a different library?

The sharing of photos for some purposes can only work with one Library at a time, whether Aperture or iPhoto. This is different than with the Media Browser, where more than one library can be seen. There is a file (iPod Photo Cache) that is singular in it ability to reference a library. This controls such things as sharing to an Apple TV, or iTunes in my experience.

Your creation of different libraries is involved in what you have experienced.

Ernie

So in the primary user account (the one with the problems) if you open Aperture does the shared library open by default?

If not, if you double click the shared library does Aperture open?

Share previews with iLife and iWork needs to be enabled in Aperture's preferences to be able to see Aperture images in the media browser. If you deleted the Aperture .plist file it should have defaulted to enabled. But check it anyway.

Try this. In the account that is not working create a new empty library and import a few images into it.

How try looking at iMovie (or whatever else is having problems) and see if you can see Aperture.