When a friend log in i have internet explorer was getting mixed content warnings : "Do you want to view only the webpage content that was delivered securely?". Also in chrome and firefox.

My website is configured for full ssl support.

can you provide a link to your website with 2 dummy accounts(send these via 'contact us' form).
I ll have a look on what is happening.

Thanks for the support now your gravatar fix solved 90% of the issue. But now sometimes the ie8 dialog box come back. Much less than before. Difficult to say under what conditions. It must remain a last request unencrypted in http ...