Steps to reproduce:
1) Create container with two components. One wich can get focus (e.g. JTextField) and JTabbedPane.
2) Add some components to JTabbedPane so it has at least two tabs.
3) Now set focus to the first component, which isn't the JTabbedPane (e.g. the JTextField).
4) Let say the JTabbedPane has selected the first tab.
5) Now if you select by mouse the unselected (i.e. the second tab), the tab gets
selected, but the focus remains in the JTextField!!

On the other hand if you under the same condition click on the selected tab, the focus is transferred. The transferring of the focus by clicking on unselected tab, seems to be working only if the focus is already in the JTabbedPane.

(I can reproduce this on linux and solaris, expecting it is also at windows).