Zend AMF working for personal site but not client's

I'm a little new to sending info back and forth between Flash Player, PHP, and a mySQL database.

I'm using Zend AMF to talk to a database, pull info, and then send that info back to flash. It works great for my personal site, but I'm doing a similar action for a client and it's not working whatsoever. I get the Bad Call error when it tries to access the endpoint page.

For testing purposes, I've kept the code identical so the only thing I can think of that is causing the problem is that the client's site requires a username and password to log in before accessing any content.

Is there something I'm missing that will make this work? Is there any more info I should post that could help decipher this issue?