[Zope-CMF] Cookie Crumbler Weirdness

[HoYin Au]

On a particular installation of CMF Site (there are other CMF sites on 
the same server, but they don't exhibit the same problem) - when I 
attempt to log in, it verifies the login as ok but doesn't set any 
cookies beside __ac_name ... this happens on different computers with 
all types of browsers (Netscape 4.79, IE 5.5, IE 6.0, Mozilla 0.9.8).

Is there a solution to this?

Setup:
Apache 1.3.23 w/mod_proxy
Zope 2.5.0
CMF 1.2
Using SiteRoot