[Alan Anderson]

If you truly haven't changed anything, that error should not be possible. Begin, Teleop, and Finish all use the same name for the one joystick Refnum used in the program.

How are you running the code?

Since you mention probing values, I assume you're clicking the Run arrow at the top of the vi window. In order for everything to work properly, you must run Robot Main. It will call all the others (Begin, Teleop, Periodic Tasks, etc.) as necessary.