That message is from my Anti-Malware Plugin (GOTMLS). It is pointing out that another plugin (probably wp-facebook-open-graph-protocol) is using an output buffers handler that controls the delivery of content and usually prevents dynamic long running plugins, like mine, from returning any content until the process is complete. This means you may not see any results from my scan until it finishes (assuming it can finish), and it may look like it's broken or doing nothing at all. I would recommend disabling the other plugin (again, probably wp-facebook-open-graph-protocol) while you are running the scan. Then you can turn it back on when you are done scanning.
I don't know about Wordfence but there's probably no conflict there. Wordfence and GOTMLS have always seemed to work together just fine.
Sorry for the delay in responding, I never got a notification of this post from wordpress.org (I usually do and then reply right away). Let me know if I can be of any further assistance.