[Plugin: Application Maker / APM – CRM edition] 'Headers already sent' error.

On plugin activation, WordPress triggers an alert:

“The plugin generated 8 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.”

Plugin then generates headers already sent errors during the course of operation.

http://wordpress.org/extend/plugins/application-maker-crm-edition/