Forum OpenACS Q&A: Response to no headers from ns_return!?
Expires:headers? Those two commands worked for me:
ns_set icput [ns_conn outputheaders] "Pragma" "no-cache" ns_setexpires 0
Also if you have control over the referencing link then you can append a bogus variable with some random value to the url to make sure IE really reloads the page (very ugly though ...)