[Zope] Moving from Linux to FreeBSD - problems with old Zope instances

[Gitte Wange]

Hello,

I'm about to migrate a server from Linux (Mandrake 9.2) to FreeBSD-5.2.1.
I have moved my Zope-2.7 instances without a problem.
Now ... my 2.6.1 instances are not migrated very well. Some of them runs 
like a charm. Others core dumps when you access the sites for the first 
time.
The same goes for one of my two 2.5 instances. It just crashes when the 
site is accessed for the first time.

Now I suspect python to be the problem here. With Zope-2.7 you needed to 
compile python with bigger thread size on BSD in order for it to work.
Do I need to compile python with anything special to make them work with 
older Zope instances (I'm using python 2.1.3 for this).

I really don't get this but I'm sure there is some reasonable 
explanation once I figure out what is happening :-)

Greetings,
Gitte Wange