Tested with the following environment:
* Product Version: NetBeans IDE Dev (Build 200807101204)
* Java: 1.6.0_10-beta; Java HotSpot(TM) Client VM 11.0-b11
* System: Linux version 2.6.24-19-generic running on i386; UTF-8; en_US (nb)
* Userdir: /home/josin/.netbeans/dev

There are components without LABEL_FOR which are pointing to it:
 * "Switch between updates, available, installed and downloaded plugins | Switch between updates, available, installed
and downloaded plugins" TabbedPane
 * org.netbeans.modules.autoupdate.ui.UnitDetails { Plugin Details | text/html } 
 * org.netbeans.modules.autoupdate.ui.UnitTable { List of Plugins | List of Plugins }

Full output from accessibility tester:

=========================================== Tested Window title : Plugins ===========================================

Doesn't implement Accessible :

Class
    javax.swing.plaf.synth.SynthSplitPaneDivider { } 
Class
    javax.swing.plaf.synth.SynthSplitPaneDivider { } 
Class
    javax.swing.plaf.synth.SynthSplitPaneDivider { } 
Class
    javax.swing.plaf.synth.SynthSplitPaneDivider { } 
Class
    javax.swing.plaf.synth.SynthSplitPaneDivider { } 

No Accessible name : - none.

No Accessible description : - none.

Label with LABEL_FOR not set : - none.

Components with no LABEL_FOR pointing to it :

Class
    javax.swing.JTabbedPane { Switch between updates, available, installed and downloaded plugins | Switch between
updates, available, installed and downloaded plugins } 
Class
    org.netbeans.modules.autoupdate.ui.UnitDetails { Plugin Details | text/html } 
Class
    org.netbeans.modules.autoupdate.ui.UnitTable { List of Plugins | List of Plugins } 

Components with no mnemonic : - none.

Components with wrong mnemonic (mnemonic isn't ASCII , label doesn't contain mnemonic): - none.

Components not reachable with tab traversal : - none. [Evaluation: