Make sure you are following our Authorize.Net integration instructions:
http://www.e-junkie.com/ej/authorize.net-shopping-cart.htm
If you are copy-pasting your API Login ID and Transaction Key from Authorize.Net into your E-junkie Admin, make sure you are not including any extra leading/trailing spaces nor other extraneous characters.
(P.S. For security's sake, I deleted the Transaction Key you posted above; you should not reveal that Key anywhere the public can see it. :^)