Partially Encrypted Message in Firefox only

I have installed Secure Pages module to direct visitors to https only on the checkout portion of my website and I am getting a "Connection Partially Encrypted" message when using Firefox only. I have tested it in IE, Chrome, Safari and it works fine. The odd part of Firefox is when I turn off the module and manual add the https in the address bar it does not get the "Connection Partially Encrypted" message and it fully recognizes the security certificate. I have tested this on other pages outside of the shopping cart as well and I get the same result.