Cant Get UPS & USPS To Work Together

For some reason I cannot get the UPS & USPS shipping methods to work together. If I disable one, the other one works fine, but when I enable them both nothing happens when I try to go to the "Select Shipping Method" step and it just sits there. Any ideas? Using OpenCart version 1.5.1.3.

Thanks,
-Tim

So. Its been almost a month and no one knows how to fix this issue? ANYONE have any ideas?

I am having the exact same problem. Have you had any luck fixing this one?

Same problem here.