Key-Navigating on consecutive Popups not working(Nifty-GUI)


in my menu i have Popup to Log in to a Server. On this Popup there is also a Button to get to the Register-Popup. When you click this button this Code is executed:
The new Register-Popup appears correct, but you cannot use Keys to navigate through it as normal (for example “Tab” to focus the next element or “Enter” to click a Button).

Any ideas how i can fix this?