Project Builder lets you make frameworks, which is the preferred format for shared libraries on Mac OS X. Apple has docs about it, or grab something like the Quesa source (
www.quesa.org), which has a PB project you can examine. I myself don't know enough to give you a detailed answer yet.
Your error means you are accessing memory which you don't have permission to touch. Likely causes are uninitialized pointers or an object that wasn't retained properly.
Brent