In the sample-config.tcl that comes with aolserver, extensions are preceded by a dot "." in the ns/encodings section:
ns_section ns/encodings
ns_param .adp "utf-8"
ns_param .html "utf-8"
maybe that's the reason (I don't use that section myself and get my adp files in utf-8 with no problem).
If it still fails after that, check again the encoding of your adp file just in case.
