AutoCad 3D :: Unable To Draw Simple Vertical Lines In Z-axis

I'm working in ACAD 2012. I am at times, unable to draw simple vertical lines in the z-axis. Drawing pluming riser diagrams in 3D. Steps I am taking,

1) Opening the drawing.
2) X referencing a floor plan.
3) Changing the view using the cube to SW Isometric
4) Using the LINE command selecting a point, aligning the cursor with what seems like the Z-axis and entering the distance, heighten enter.

The line drawn is flat. This line can be seen as flat when rotating views. The only solution I have found is to use the "Reset Autocad Settings to Default"

Observations: Sometimes I am able to draw in 3D just fine, but something will happen in the middle of the drawing process that will now only allow me to draw flat. Also was never able to draw polylines in 3D is that how it's supposed to be? Used another computer with the same drawing, at first won't allow me to draw in 3D but after a couple attempts will eventually draw in 3D just fine. Tried starting from a blank template, no luck. Tried changing drawing space to 3D modeling and 3D basics, no luck. Also, when working drawings with existing 3D objects, I am able to snap to vertical point as a start point but cannot snap to a point on any other points on the object that at are at a different elevation.