We tracked this down. The default value for the parameter
ShowContextBarP in acs-subsite.info was 0 on the HEAD so if you
installed from a HEAD checkout you did not get context bars. This had
been fixed on the oacs-4-6 but the fix had not been merged back to the
HEAD (it is now). If anyone else sees this problem they should be able
to fix it by going into the site map and changing this parameter for
the main site (and any other subsites mounted). You could also edit the
default in apm.
