you have config->wordprocessor listed as config->word_processor preventing the .doc extension from coming out on invoice files.... Justin, sorry I would have just fixed it myself but I have forgotten how to get onto the source....
About the issue with the missing "doc" its fixed by going to \simpleinvoices\templates\default\invoices\quick_view.tpl and go to line 22 col 271 and then change $word_processor to $wordprocessor
