I just had a very similar problem. I use a fresh Ubuntu 8.04 and the
OpenACS-Ubuntu Package.
For me, un-commenting the line
#ns_param map "/*.html" ;# Any extension can be mapped
did the trick. But maybe this has other unwanted implications?
#---------------------------------------------------------------------
#
# ADP (AOLserver Dynamic Page) configuration
#
#---------------------------------------------------------------------
ns_section ns/server/${server}/adp
ns_param map /*.adp ;# Extensions to parse as ADP's
ns_param map "/*.html" ;# Any extension can be mapped
ns_param enableexpire false ;# Set "Expires: now" on all ADP's
ns_param enabledebug $debug ;# Allow Tclpro debugging with "?debug"
ns_param defaultparser fancy
ns_section ns/server/${server}/adp/parsers
ns_param fancy ".adp"
ns_section ns/server/${server}/redirects
ns_param 404 "global/file-not-found.html"
ns_param 403 "global/forbidden.html"
