[Zope] Restarting Zope makes Values in python class disappear

I've got a simple python class that has a data member that holds a list of strings (among other things). I can laod values into this list fine. And can query the object and the list is populated. However, after I restart Zope, the list for the class instance is empty. The other data values in my class retain their values just fine. I've got other classes that hold similar lists for which this doesn't occur. I'm banging my head against a wall - any ideas? mark@ifopen.com