Hi Brian, yup I used the file you posted and it worked fine over here.

Also your second file works fine over here as well.

I think the problem you are running into is that you are selecting the original curve objects that you used to extrude, instead of selecting the edges of the solid.

Since those curve objects are in the exact same location as the edges of the solid, it is easy for them to get selected when you click in that area.

So before you do your fillet, select those curves (and in your new file you actually have an extra planar surface object down there as well) and hide or delete them so that when you click to select the pieces to fillet you will be targeting pieces of your solid and not those original curve pieces.

Another way to make this clearer - click and drag on the solid to move it a little bit off to the side, and you will then see these other objects that are getting in your way.

- Michael