If you opened a new file and tried making various objects, then I don't think having a reference layer would be the problem.
But to check, the layers are on the bottom part of the channel box on the right side of the screen. You can access it by clicking the rightmost of the three buttons on the top right of the screen. Mouse-over, it should say channel box.
Anyway, if there are any layers, they will show up in the bottom section and they can be a template, reference, or none, in which case one of the boxes to the left of the name will be an R, a T or showing nothing. There is also a visible, non-visible option there (V or nothing, I think) fyi.
So I don't think that would be the problem, but that's how you can check.
Oops, Brain posted while I was...