If you have a secure (SSL) page but are receiving a security warning on it, it is most likely because it contains non-secure content.
Typically non-secure content can be either images or scripts running on the page which are being retrieved from a non-secure http: address.
Look at the code on those page and check for the following:
- search for img tags. Make sure that the 'http' address in an image tag is actually using 'https' (a secure page)
- search for script tags. Make sure that any addresses are also using https: in the front of the URL