Converting latin1 to utf8 in WP 2.5

Is there a way of converting the latin1 database to utf8 in WP 2.5?

I was successful in an earlier version of WP but I have one site left to convert and I’m successful.
I get the error:

Invalid argument supplied for foreach() in /home/asefalkm/public_html/56/wp-includes/capabilities.php on line 31