Quote Originally Posted by jolion View Post
I installed the latest version of OPC

When submit the confirm button it goes in a loop and the checkout one page shows the message "Your order's details have changed. Please review the current values and re-submit". I read several messages about the same problems, but with no result. I really want to use OPC, so any help is welcome.
What Zen Cart version? What template are you using? What shipping, payment and order-total modules?

If possible (i.e. you're not testing on a local computer) could/would you post a link to the site? If you don't want it public, you can send me the link via PM.

Please note that the message you identified can result from a bunch of different underlying issues.