A day or two after my original posting I came back to this and tried something different which seems to have worked - adding the subsite node to URLs.
if {[ad_conn user_id] == 0} {
ad_returnredirect "http://myintranet.com/intranet/register/?return_url=/intranet/"
}
where /intranet/ is the ACS subsite which the host-node directs myintranet.com to.
After seeing Bruno's postings this morning, I went back and experimented again and now it seems to work no matter what I try, be it ad_maybe_redirect_for_registration or any combo of URLs in my own user_id test. In the intervening period, I've moved developement from Oracle to Postgresql (clean 4.6.2 ish CVS install) so I'm really clueless at this point as to what's going on. I'm happy things are working but I'm curious if any changes were made to the request processor that would have affected this between 4.6.1 and 4.6.2.
