To reproduce:

1) Unzip the TabPaneBug NB project and setup the sdk.jar in project libraries
2) Run
    => application opens a window (see TabPaneBug1.png)
3) Click on "Move last tab to first position" button
    => application moves Tab #3 to first position
    => Tab #3 disappears (see TabPaneBug2.png)
4) Click again
    => Tab #2 disappears (see TabPaneBug3.png)