Hi Steve, it's because you're trying to extrude only single lines. A single line all by itself does not really define a unique plane, there are an infinite multitude of planes that go through it at different rotations.

When there is not a unique planarity to an object it will default to extrusion in the z axis - that's how it has always worked, it's not any setting that has been changed.

When there is no automatic plane that can be determined for an object you need to push the "Set dir" option if you want to change the direction of extrusion.

Lines along the x and y axis directions are particularly troublesome because not only do they not themselves define a single unique plane, but they're also simultaneously on the view planes of multiple ortho views as well, like a line along the xaxis direction is on both the Top view's drawing plane and also on the Front view's drawing plane at the same time.

- Michael