I found a patch that works for me for now.
I replaced line 939 in aioseop_sitemap.php.
Was:
echo '<?xml-stylesheet type="text/xsl" href="' . $plugin_path . 'sitemap.xsl"?>' . "\r\n";
replaced with:
echo '<?xml-stylesheet type="text/xsl" href="' . str_replace("https","http",$plugin_path) . 'sitemap.xsl"?>' . "\r\n";
Seems like it could work as a permanent fix. In the case that someone is logged in via http it still works. And, I can't see why someone would want to use an ssl link to their sitemap or the .xsl stylesheet in the sitemap anyway, though I guess there could be a special case.
