If you are getting "mixed content" warning, please check if all rows in the wp_options table use the correct https:// URL. You can quickly find the offending rows with this SQL query:
select * from wp_options where option_value like 'http:%';
Once you've ensured that there aren't any http:// URL left, please click "Clear Cache" from the VamTam menu in the admin bar (or click "Save Changes" in VamTam/General). This will regenerate the cache/all.css file.