Issue: After some time, AFP access to a certain shared folder on a QNAP device would fail. Finder would be able to navigate to the QNAP via AFP, but when attempting to mount the share, it would attempt to connect for a minute or so, then fail with error message:...
Important!
Make sure you backup your data and system before carrying out any steps noted here!
These steps have worked for me, but I cannot guarentee they will work for you!