404 when clicking on a page to edit plugin errors

Hi guys,

When I try to view the page/post editor I receive a 404.

I have tried disabling all plugins and the problem persists so it does not appear to be a plugin at fault here.

I have tried changing the theme to the default twenty eleven and the problem persists.

I also tried changing the permalinks to the default and the 404 still persists.

Here is the error message displayed when I try to make changes to the settings of a newly installed plugin, I am unsure if this error occurs to plugins that are already installed.

warning: Missing argument 2 for DecisionTree::on_update_idonated() in /home/iasservicesorg/public_html/wp-content/plugins/sidecar-decision-tree/DecisionTree.php on line 407

Warning: Cannot modify header information – headers already sent by (output started at /home/iasservicesorg/public_html/wp-content/plugins/sidecar-decision-tree/DecisionTree.php:407) in /home/iasservicesorg/public_html/wordpress/wp-includes/pluggable.php on line 1179