Check out with USPS enabled breaks out of the checkout box

[hfoxonline]

Hello,
I've recently installed USPSv5.0 module on my site and I'm having a problem. I'm not sure if I can adequately describe it, but I'll try. I have checkout enabled to appear in the pop-up box and currently is set to work in three different steps.  The first step shows the order contents and shipping/billing info.  When the user clicks next to select shipping method, the choices (USPS) appear, but instead of in the grey box window, you get a page from the website with the shipping choices present.  The rest of the checkout then proceeds from this page of the website. I'm not sure how to fix this so that everything proceeds from the grey box. Any help would be appreciated.
Thanks

[lowmips]

Hi,
First of all, please always post USPSv5 specific issues in the USPSv5 thread.  I am subscribed to that topic and receive notifications when new posts are made.  I only browse the main forum when I have a lot of spare time, and miss a lot of these posts.

Now, what do you mean by this:

I have checkout enabled to appear in the pop-up box

Are you using some type of modification? Screen-shots would help.