I recently was using iPhoto on my Mac Powerbook, and received an error:

An error occurred while trying to save your photo library.

It also said:

Some recent changes may be lost. Make sure your hard disk has enough space and that iPhoto is able to access the iPhoto Library.

I was lost about what to do. Luckily I found this post about the issue.

As instructed, I…

1. Downloaded BatchChmod.

2. Using this software, I applied the settings below to my iPhoto Library Folder.

Image Source

These steps worked great. I no longer have the annoying error message.