[Zope] losing random session data

[Norbert Marrale]

In Zope 2.7.5-final, python 2.3.5, freebsd6 with Transient Object 
Container settings:
Data timeout: 20
Timeout resolution: 20
Maximum subobjects: 1000

and a python script that does this:

req = context.REQUEST
prev_order=(req.SESSION.get('order'))
if prev_order == None:
   order=[]
else:
   order = prev_order
order.append(req.form)
req.SESSION.set('order',order)

my data ends up looking like this:

order [{}, {}, {'foo': '1', 'bar': 'a'}, {}, {'foo': '2', 'bar': 'b'}, 
{'foo': '6', 'bar': 'z'}, {'foo': '1', 'bar': 'a'}]

I've seen  http://mail.zope.org/pipermail/zope-dev/2006-July/027890.html
and am aware that related bug existed prior to 2.7.1.

I've used sessions without problems before, this is the first time I 
attempt to store variables in containers. What am I doing wrong?

Norbert