Help with Sessions

I have written a somewhat complex system that passes classes around through the session in my application. These classes then return references to other classes they encapsulate. For example, Class A may have an array of Class B. It news' the array of Class B on construction and then simple returns a reference to the given element from the get method. This allows me to carry the values in Class B from page to page.

My problem is this, I have reached a point "all of a sudden" in which my script is timing out. In the debugger, I am finding that it is timing out on session_start() immediately following the require_once( CLASS.PHP ) call.

In the past I was bitten by something similar - constantly registering a variable which was a reference to a class over and over again.

I am not certain of what is actually happening at this level in the session. Can someone please shed some light on this subject.

Thank you very much!

Bryan