Your OSNAPS are incorrectly set or you are not using the correct technique to pick node points.
Solution: First check your OSNAP settings. At the bottom of the screen, right click over the OSNAP button and click on "Settings". Only the "Node" snap should be checked.
When snapping to the node of an object, resist the temptation to try and pick the point directly with your cursor, as there may be many other node points in the same vicinity. The correct way to snap a node point of a beam for example, is to touch part of the beam (in a place where you are unlikely to touch another object by mistake) and the snap point will automatically jump to the node nearest the end of the beam you are touching. This is indicated by the appearance of the node symbol (a crossed circle) at the actual node point, and the text "Node" appearing next to your cursor. | 
