Ok, I had to debug uc_cim to find out what was happening...

1. In the uc_cim_charge function, in the response processing, it's checking for $response->messages->code as opposed to $response->messages->message->code which is what's returned from Authorize.net

2. Also in the same section of code, this statement...
$directResponse = split('\,', $response->directResponse);
Does not work for me. I had to change it to...
$directResponse = explode('|', $response->directResponse);
Which correctly parses the return from Authorize.net

This is version v0.6

Not sure why things are different now. Perhaps a change in the results from Authorize?