seedseller: Try it with one of the standard Drupal themes. Since shipping quotes use AJAX, it's maybe possible that your theme might not have the markup that jQuery expects, so it doesn't know where to insert the shipping quote on the page?

With build 748 you should now be able to see the request sent to the USPS server as well as the response. Since you're getting a valid response (as shown by your debug), you must have sent a valid request, but it will confirm that you're using the version of the module that you think you're using...

I guess there's nothing left to do but start inserting print statement to see where things break down. In uc_usps.module, find the function uc_usps_quote and insert "drupal_set_message(var_export($services, true));" right before the "return" statement. You should see a raw dump of an array containing elements for the USPS shipping methods you have enabled and the prices etc. for each of these methods. If you see that, the problem isn't in uc_usps.module. Then we will have to delve into uc_quote and the JavaScript that does the AJAX call...

What brand and version of browser are you using? Can you post a URL so I can see the results of requesting a quote on your site?