On Java 7b121 the tabs of a JTabbedPane in scrollable mode don't appear - only the tab text is painted. You can simply check this by setting the Nimbus LaF.
If the issue persists with the latest build, please report a bug at http://bugreport.sun.com/bugreport/ .
Dalibor Topic, Java F/OSS Ambassador, Java Products Group, Oracle
Your use of this web site or any of its content or software indicates your agreement to be bound by these Terms of Participation.
Copyright © 2014, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.