Okay, figured out how to enable/disable courier (it was a matter of switching from 3rd personn to 1st, thanks for the suggestion!), but that didn't work. On the upside, I did figure out which mod was causing the courier issue in my case. The "To Have & To Hold - Marriage Mod" has not been updated since mid-May and therefore is clashing with 1.6's changes. At present, it is kind of a broken mod.