table names should be enclosed in {curly_brackets}

Is:

function _paypalnode_get_cck_fields() {
...
  $q = db_query("SELECT nf.field_name, nf.global_settings FROM node_field nf

should be:

function _paypalnode_get_cck_fields() {
...
  $q = db_query("SELECT nf.field_name, nf.global_settings FROM {node_field} nf