I've installed a USPS module, plugged in all the info they ask for. When you try to checkout in the cart it goes to a blank white page. I've uninstalled and tried it again and it the cart works with UPS or free shipping, not with USPS. I've uninstalled the files and tried a different USPS module and get the same white page.

PLEASE HELP.

Using a template, I've used it before without any issue.