Where is your second library located? On an external volume? The Aperture Library needs to be on a locally connected volume, formatted MacOS X Extended.
Aperture: Use locally mounted Mac OS X Extended volumes for your Aperture library:http://support.apple.com/kb/TS3252
file system of the library's volume is not supported
But what is the type of the file system on your external raid?
What does Disk Utility show? (Disk Utility is located in the Utilities folder in the Applications folder)
Select your drive in the left column of the window and click the "First Aid" tab. The file system will be displayed at the bottom of the window.
Thank you for trying to help, the RAID does not show up in the disk utility screen. See below, for a shot of the drive in finder. When I set up the Synology drive, I did so from this imac and would have used a mac format since this is the only computer that the drive has ever been used with. The Aperture library worked well for months, and recently stopped working and I now get the message below.
I do not know if the recent Aperture undate is to blame and if so how to get it fixed.
So your Aperture Library is on a shared network volume? Then you have been lucky, if it worked before. The Aperture Library should reside on a locally connected volume - it is not guaranteed that network access will work, sorry. As I pointed out before, this is what Apple recommends:
Aperture: Use locally mounted Mac OS X Extended volumes for your Aperture library: http://support.apple.com/kb/TS3252