Wizard Control's NextButtonClick Event Fires One Time Only?

I have a Wizard control with 5 steps.  I have a NextButtonClick event that I want to use to run different code scenarios depending upon the ActiveStepIndex value.
One the first step (ActiveStepIndex = 0), when the user clicks on "Next", the NextButtonClick event fires as expected.  On the second step (ActiveStepIndex = 1), when the user clicks on "Next", the NextButtonClick event doesn't fire and on postback, the wizard comes up on the first step again (ActiveStepIndex = 0).
I switched the wizard control's second step's "StepType" property to "Step" from "Auto" but that didn't change it. I also added, OnNextButtonClick="wizAccountSetUp_NextButtonClick" to the wizard but that didn't change anything either.
Any ideas why the NextButtonClick event would fire only on the first "Next" button click and not the one after that? And why would the ActiveStepIndex be set back to 0? ...