Check out this post from 5 months ago... Haven't looked into it yet.
Just found
it.http://community.developer.authorize.net/t5/Integration-and-Testing/404-error-returned-from-Authnet-s-CIM-testing-transaction-server/td-p/14464
Obviously Authorize doe...
Yes. I just had it at 12/20/11 at 11:34am EST for about 2 minutes. I
also had a customer email in a complaint becuase they where also getting
a 404. That was sometime shortly before 11:05 pm on 12/19/11 (not sure
of his timezone). He said he then tri...
We just had it happen again in IE 8 at 12:05pm EST. By the time someone
came back to me 2 minutes later and I tested it worked. We are using
https://secure.authorizse.net/profile/manage