Unfortunately the description of your issue is not enough clear. The plugin normally should not affect the post editor, nor the screen options.
As for Ajax usage, it depends on WordPress and not directly on the plugin, which has an adaptive behavior. Normally WordPress makes heavy use of Ajax for widgets operations, but you may revert to “Accessibility mode”, which is not based on Ajax. You may switch the “Accessibility mode” from the screen options in the widgets page. If you’re unable to reach that option because of the above issue, you may open the following url by hand: http://www.your-domain.com/wp-admin/widgets.php?widgets-access=on