For anyone still having the problem coppercup mentioned, you need to go into your .htaccess file and edit the line:
remove the # and put in the base directory of your install:
(Also, I suggest not using JWait's provided auth.php file, which will cause the expiration_date error mentioned upthread; this module can patch the auth.php file of a
freshly installed X-Cart 4.1.11 correctly.)
Thanks for all the discussion in here, though, everyone, and the prepatched files, JWait; it was a big help for me in getting this module working.