40 second polling seems ... very high. Unless the network-link to each device is extremely limited, a regular server polled should be done in under 10.
Are you using the poller-wrapper?
With the default of only 2 threads and 40 +/- servers, taking 30-40 seconds each - you'll exceed the 5 minute interval for statistics-gathering easily.
You could try increasing the number of parallell threads used for polling.
Perhaps I'm overlooking the obvious but I saw no daemon to restart and I even went so far as to reboot the server...
How does one reload the config file after making changes?
http://www.observium.org/docs/config_options/
...makes no mention of reloading aside from specifics about syslog...
Thank you for your assistance