Sure enough, a quick change to adp_parse_ad_conn_file made all the difference in the world. I added the following two lines:
ns_set put [ns_conn outputheaders] "Cache-Control" "no-cache"
ns_set put [ns_conn outputheaders] "Pragma" "no-cache"
And everything now seems to work just fine.
Is there any reason why this should not be a standard part of OpenACS?