I was also unable to get to any of the sites on my network. It was the only upgrade I did today. It was the only thing I did today. When I removed the plugin. Everything came back up.
I then reninstalled it and everything works. The errors in my logs stopped too.
Over 20 of this message-
[13-Aug-2012 19:35:36] PHP Fatal error: Call to undefined function sfw_add_default_pwd_style() in /home2/xxxx/public_html/xxxx/wp-content/plugins/spam-free-wordpress/tl-spam-free-wordpress.php on line 130