JInternalFrame makes the parent panel lose track of MouseWheelEvent?

I have a JDesktopPane which default layer is a JPanel rendering custom Java2d by overriding its paint() method. When the user clicks a rendered object, I open a JInternalFrame displaying details. The user can additionnaly pan and zoom with a mouse pointer or mouse wheel change开发者_运维百科.

The weird thing is that after closing the last JInternalFrame, mouse control changes: mouse pointer can still drag, but mouse wheel does not react anymore. In other words, mouseWheelMoved(MouseWheelEvent e) gets never called, but mouseMoved, mouseClicked, mouseDragged and mouseRelease still get called properly.

The JInternalFrame displays a JTable in a JScrollPane. Would somehow the JScrollPane acquire the wheel?