Locked out of site with supporter error message


My last 3 developers quit blaming it on supporter.

I've just hired someone who has been activating all the plugins which come in the pre-installed kit and the site has gone down.

I orginally received the 404 error message, then 'you are locked out' now I get:

Fatal error: Call to undefined function writeToLog() in /home/explorfw/public_html/wp-content/mu-plugins/supporter-amazon.php on line 30

Can you help?

Many thanks,