yarpp causing formatting.php warning

Hi reader!

I have just moved my blog to a new URL.
Everything is fully OK, working and all, but if I go into any of my posts, I have a warning message at the beggining right before the body of the text saying: Warning: strip_tags() expects parameter 1 to be string, array given in (root, changed it)/html/wp-includes/formatting.php on line 631

Now line 631 is the following:

629function sanitize_user( $username, $strict = false ) {
630 $raw_username = $username;
631 $username = strip_tags($username);
632 // Kill octets
633 $username = preg_replace(‘|%([a-fA-F0-9][a-fA-F0-9])|’, ”, $username);
634 $username = preg_replace(‘/&.+?;/’, ”, $username); // Kill entities

I figured that if I switch off YARPP then this message disappears, but I would really want to use YARPP since I was happy with the plugin so far.

Any idea what to do to get rid of the messages.