[mod_python] Seg Fault when using session object

Hello,
I've got this simple piece of mod_python/psp; If I uncomment the foo=session 
line I get a seg fault. Has anyone seen this before and can direct me towards 
finding out what the problem is please?
I'm running Apache/2.0.50, mod_python 3.2.8 and Python 2.4.
I've confirmed that it isn't the known expat and mysql/php problems.

<%
#foo = session
done_login = False
if(form.has_key("username")):
	username = form["username"]
	password = form["password"]
	req.write("%s" % (username,))
%>

Cheers,
Emlyn.