Hi guys,
I'm probably not the first one to report this, but regarding the:
warning: htmlspecialchars() [function.htmlspecialchars]: Invalid multibyte sequence in argument in /home/virtualmin/public_html/includes/bootstrap.inc on line 860.
user warning: in /home/virtualmin/public_html/includes/cache.inc on line 108.
message on the user account page when you're not logged in, it's sometimes fixed with the Transliteration module. Transliteration is a great module for anything file upload related and from memory, has the power to transliterate files that were uploaded previous to enabling the module.
Cheers, Josh