I´m not at home and so I don´t have Maya on the desktop.
But the good thing in Maya is that you have very much ways to get what you want.
Attach your circle to motion path(which is your curve) and set a time line value of 30 frames (start, end) (I think!)
Duplicate the circle along the curve and loft them. When you get a wrong result check the normals that they are all in the same direction, or highlight the circles one by one from the first to the last and loft again.

I think you will ask where the option is to duplicate along path. Its in the same tab where you did find the extrude along path option. I think it is called duplicate along path.
I hope I said nothing wrong...:p