Double-click on JPanel resizes fields

Perhaps one of you might have dealt with this problem before...

I have a JPanel that contains multiple text fields and a JList. I noticed (accidentally) that when I double-click on the JPanel, the JList and one of the text fields shrink to a smaller size. Note, the JList only resizes when there is something actually listed inside it. It's as if the field is resizing to take the width of the text inside of it. When I remove the text from inside the JList and double-click the JPanel again, the JList goes back to its original size. The text field only resizes when it is empty, however, and only goes back to it's original size when there is text inside of it. There are other JPanels that do not have this problem. I've compared those with this one and have been unable to find a difference.

Any thoughts?