Take a look at this post. Keep in mind nspostgres is a database driver and not a typical AOLserver module. It should load in the database driver section of nsd.tcl (aolserver config file) and not the modules section.
Sorry, I linked back to your post! I meant to link to this post. But I just reread that post and it doesn't actually say how he fixed it. You need to add
ns_section "ns/db/drivers"
ns_param postgres ${bindir}/nspostgres.so
to your nsd.tcl config file. And not add
