From the screenshot it is not possible to tell whether the problems Box and Cotty raise are the cause of your problem, as nothing visible gives size of the model or units settings. It is also not possible to tell what inference engine markers you may have seen while you were drawing your line. So here’s an alternative explanation if you did not pay close attention to them.
If you move the cursor out from the start toward the desired corner, it will first pass close to the wrong corner and the inference engine will mark that corner. If you click while that marker is displayed, the end of the line will snap there. But if you continue to move the cursor out toward the other corner, the inference marker should eventually move to it. Then when you click, the line end should snap there.
As another technique, if you really want the line to be along the red axis, you could start it in that direction and then hold down shift to lock the direction while you continue to move the cursor to the endpoint. No matter where you click, the edge will be created parallel to the red axis.
By the way, nothing about this changed from 2014 to 2015.