UPS and USPS shipping modules conflict?

I am trying to use both the UPS and USPS built-in shipping modules, but when I enable them both, I get no response after I click the "Get Quotes" button on my shopping cart checkout page.

I have now just successfully get my USPS account to be activated, and if I use them separately one at a time they work. If I want to give users the option of either USPS or UPS, I can't.

Also I was wondering if their was a free Fedex extension that does the same exact thing as both of the UPS and USPS modules. Thanks for your help everyone.

Version: 1.5.1.3
United States Postal Service

I just asked that question! Here was the reply:
http://forum.opencart.com/viewtopic.php?f=161&t=42226

Thanks. Works now.