Well, part of the problem could be that the emulator doesn't work exactly like Authorize.net works. To take a look at this, you would want to print out the Authorize.net request and response:
<br />The Authorize.net full requst is: <?php echo(AuthNet_Result("Full Request")) ?><br />
<br />
The Authorize.net full response is: <?php echo(AuthNet_Result("Full Response")) ?><br />