after I added a new folder (modules) in Site/default and moved some downloaded modules into this new folder I got this message. Tried the link, but get the message that this page can't not be found. I tried to follow some older posts, but could not get any further. Any help and advice will be greatly appreciated. I'm very new to this.

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'nodereference_autocomplete_access' was given in /home/fuseitgl/public_html/includes/menu.inc on line 452.