sharing iPhoto library between users on same imac
I just updated to the latest iphoto (9.5.1). Previously, I've had the library located in a shared directory and each user on the computer used that library. Now with the update, I get an error that I don't have the correct permissions. iPhoto prompts to fix it, but then is unable to. If I rebuild the library, then the other users do not have the correct permissions. The permissions for the file itself is set to read and write for everyone. I don't want to waste hard drive space with 2 or more full libraries that are all identicle. Is there a setting somewhere I'm missing?
iMac (21.5-inch Late 2009), Mac OS X (10.6.8)