If you want your services to be accessed by your Silverlight applications using https protocol using this on your clientaccesspolicy.xml file won’t be enough.

<domain uri="*"/>

According to MSDN you have to specify the protocols you want to support, like this:

<?xml version="1.0" encoding="utf-8"?>
<access-policy>
    <cross-domain-access>
        <policy>
            <allow-from http-request-headers="*">
                <domain uri="http://*"/>
                <domain uri="https://*"/>
            </allow-from>
            <grant-to>
                <resource path="/" include-subpaths="true"/>
            </grant-to>
        </policy>
    </cross-domain-access>
</access-policy>

Cheers!