So I had a case of maneuver node not working a couple of times in the most current version and also in earlier experimental versions too.
I was able to place a maneuver node and manipulate it but the node would not show anything on the navball, you could only see it existing in map view.
It happened in a situation where I attempted a rescue mission for a kerbonaut in LKO. The ship was controled by a probe Probodyne HECS and had no crew or tourists only initially. It consisted among other stuff of uncommanded seats of 2 Mk 1 Crew Cabins and 1 commanded seat of Mk1 Command Pod. I rendezvous successfully with kerbal to be rescued. Moved him from debris to the ship. Make him enter the ship through Mk1 Command Pod and then moved him to one of uncommanded seats in Mk1 Crew Cabins. Then I place the node to plan a rendezvous with another kerbal to be rescued and the node doesn't work properly and behaves as described above. I had to move to Space Center and back to ship to make it work again.
I am playing in Windows 7 64 bit and using 64bit KSP client.
If the issue was previously reported I am sorry but I couldn't find it.
[Edit] I am attaching a screenshot of the issue:
It is still happening in the newest build.
