What is happening is that the node has been recently harvested. It still shows in game but as unclickable. From a distance you can hover over the node and if the "harvest" arrows show up then it is harvest able again.
Or you can sit and wait for it to reset.
When a node is harvested, it does remain for a short time but it quickly despawns. However, I experienced the bug the OP is referring to in the beta and a few times since launch. These nodes are not recently harvested because they persist in the world (they don't despawn). They appear on the minimap as resource nodes and you can see them laying there on the ground but you can't click on them or get any tooltip info when the cursor is hovering over them.