I've an Wordpress site using Wordpress e-Commerce wordpress plugin. I am using USPS shipping and predetermined fee shipping. In checkout, you are able to pick predetermined fee or usps priority mail. Should you pick predetermined fee, the grand total is up-to-date within an ajaxy way. Should you pick priority mail, the grand total changes but without adding the priority mail shipping cost.

It isn't giving me the right order total only if picking priority mail. For instance...

product cost $20.00
usps priority mail shipping $5.00
total $20.00

What's much more strange, is in the beginning the page shows the right cost, but another later changes towards the product cost minus the shipping costs.

It is something which has related to ajax, because whenever you click the radio button, it changes the grand total. So I am thinking it's most likely a javascript conflict. I've already checked several files and tweaked them however i can't have great results. I do not debug lots of javascript, so I'm not sure exactly what direction to go.

What tools can one use or how do i rely on them to discover what's subtracting the shipping cost in the grand total another following the page loads.

Your best choice is by using Opera with Firebug. This will help you to set a breakpoint within the JavaScript, and inspect precisely what it's doing, as it is doing the work. It will likewise permit you to inspect any AJAX demands and reactions.