As of 12:45 PM mountain time on Friday authorize.net is still down.  It looks like a fire caused more than a little damage and a few thousand or so merchants like us are feeling the hit.  I'm sure they are working quickly to restore service so card transactions can go through again.  Both google checkout and Paypal options are available.  

 Wait a minute...looks like transactions are starting to come through again.  Hopefully that will continue!

Oh well...enjoy your 4th of July celebration this weekend!