All of the add-ons are giving me this error when I upgraded to WP3.8:
[13-Dec-2013 14:30:36] PHP Fatal error: Call to undefined function get_plugin_data() in /home/taylorwp/public_html/wp-content/plugins/acf-flexible-content/acf-flexible-content-update.php on line 168
I commented out that line and the admin loads again. I'm not sure what's causing this error since this function is a legitimate function. I just wanted to bring it to your attention.