Warning: simplexml_load_string() [function.simplexml-load-string]: Entity: line 1: parser error : Start tag expected, '<' not found in [path]/includes/facebook/facebookapi_php5_restlib.php on line 2417

Warning: simplexml_load_string() [function.simplexml-load-string]: Got EOF while waiting for outstanding responses in [path]/includes/facebook/facebookapi_php5_restlib.php on line 2417

Warning: simplexml_load_string() [function.simplexml-load-string]: ^ in [path]/includes/facebook/facebookapi_php5_restlib.php on line 2417

Unable to add cookies, header already sent.
File: /home/sites/londonmoms/forum.londonmoms.ca/includes/class_core.php
Line: 3277

I'm getting errors like these all over the site. Multiple computers.

The top 3 are appearing in the header area.

The bottom one is appearing right within vbulletin.