bekommen immer wieder diesen Fehler,

woran liegt das ?

30.04.2013 - 22:08:09.182 ThreadGroup - Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
30.04.2013 - 22:08:09.183 ThreadGroup - at javax.swing.DefaultRowSorter.convertRowIndexToMode l(Unknown Source)
30.04.2013 - 22:08:09.184 ThreadGroup - at javax.swing.JTable.convertRowIndexToModel(Unknown Source)
30.04.2013 - 22:08:09.185 ThreadGroup - at org.jdesktop.swingx.JXTable$TableAdapter.getFilter edStringAt(JXTable.java:3138)
30.04.2013 - 22:08:09.186 ThreadGroup - at server.gui.table.TableHighlighter.highlight(TableH ighlighter.java:38)
30.04.2013 - 22:08:09.186 ThreadGroup - at org.jdesktop.swingx.decorator.CompoundHighlighter. doHighlight(CompoundHighlighter.java:234)
30.04.2013 - 22:08:09.187 ThreadGroup - at org.jdesktop.swingx.decorator.AbstractHighlighter. highlight(AbstractHighlighter.java:172)
30.04.2013 - 22:08:09.187 ThreadGroup - at org.jdesktop.swingx.JXTable.prepareRenderer(JXTabl e.java:3501)
30.04.2013 - 22:08:09.188 ThreadGroup - at javax.swing.plaf.basic.BasicTableUI.paintCell(Unkn own Source)
30.04.2013 - 22:08:09.188 ThreadGroup - at javax.swing.plaf.basic.BasicTableUI.paintCells(Unk nown Source)
30.04.2013 - 22:08:09.189 ThreadGroup - at javax.swing.plaf.basic.BasicTableUI.paint(Unknown Source)
30.04.2013 - 22:08:09.190 ThreadGroup - at javax.swing.plaf.ComponentUI.update(Unknown Source)
30.04.2013 - 22:08:09.190 ThreadGroup - at javax.swing.JComponent.paintComponent(Unknown Source)
30.04.2013 - 22:08:09.192 ThreadGroup - at javax.swing.JComponent.paint(Unknown Source)
30.04.2013 - 22:08:09.192 ThreadGroup - at javax.swing.JComponent.paintToOffscreen(Unknown Source)
30.04.2013 - 22:08:09.193 ThreadGroup - at javax.swing.BufferStrategyPaintManager.paint(Unkno wn Source)
30.04.2013 - 22:08:09.194 ThreadGroup - at javax.swing.RepaintManager.paint(Unknown Source)
30.04.2013 - 22:08:09.194 ThreadGroup - at javax.swing.JComponent._paintImmediately(Unknown Source)
30.04.2013 - 22:08:09.195 ThreadGroup - at javax.swing.JComponent.paintImmediately(Unknown Source)
30.04.2013 - 22:08:09.196 ThreadGroup - at javax.swing.RepaintManager.paintDirtyRegions(Unkno wn Source)
30.04.2013 - 22:08:09.197 ThreadGroup - at javax.swing.RepaintManager.paintDirtyRegions(Unkno wn Source)
30.04.2013 - 22:08:09.198 ThreadGroup - at javax.swing.RepaintManager.prePaintDirtyRegions(Un known Source)
30.04.2013 - 22:08:09.199 ThreadGroup - at javax.swing.RepaintManager.access$700(Unknown Source)
30.04.2013 - 22:08:09.199 ThreadGroup - at javax.swing.RepaintManager$ProcessingRunnable.run( Unknown Source)
30.04.2013 - 22:08:09.200 ThreadGroup - at java.awt.event.InvocationEvent.dispatch(Unknown Source)
30.04.2013 - 22:08:09.201 ThreadGroup - at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
30.04.2013 - 22:08:09.202 ThreadGroup - at java.awt.EventQueue.access$000(Unknown Source)
30.04.2013 - 22:08:09.202 ThreadGroup - at java.awt.EventQueue$1.run(Unknown Source)
30.04.2013 - 22:08:09.203 ThreadGroup - at java.awt.EventQueue$1.run(Unknown Source)
30.04.2013 - 22:08:09.204 ThreadGroup - at java.security.AccessController.doPrivileged(Native Method)
30.04.2013 - 22:08:09.205 ThreadGroup - at java.security.AccessControlContext$1.doIntersectio nPrivilege(Unknown Source)
30.04.2013 - 22:08:09.206 ThreadGroup - at java.awt.EventQueue.dispatchEvent(Unknown Source)
30.04.2013 - 22:08:09.207 ThreadGroup - at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
30.04.2013 - 22:08:09.207 ThreadGroup - at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
30.04.2013 - 22:08:09.209 ThreadGroup - at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
30.04.2013 - 22:08:09.210 ThreadGroup - at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
30.04.2013 - 22:08:09.211 ThreadGroup - at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
30.04.2013 - 22:08:09.212 ThreadGroup - at java.awt.EventDispatchThread.run(Unknown Source)