Forward of issue entered by NetBeans QA:
http://www.netbeans.org/issues/show_bug.cgi?id=97043

Error can be also seen in plain JToolbar in sample app, not needed to be inside NetBeans.

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NetBeans IDE Dev (Build 200702281900)
1.6.0_01; Java HotSpot(TM) Client VM 1.6.0_01-b04
Linux version 2.6.17-11-generic running on i386
en_US (nb); UTF-8

Ubuntu 6.10, default theme setting (visible also in other themes).

There are some invalid pixels and lines around draggers in main toolbar - see attached
screenshot.