exception quand le fichier devient grand

Bonjour.
j'ai un prigramme censé m'afficher un graphe de relation.
jusqu'a alors, quand je faisais mes tests sur un petit modèle, il n'avait pas de problemes.
mais dès que je lui donne un fichier important(avec plusieurs instances environ 1000 lignes), il me genere ce message:

Exception in thread "AWT-EventQueue-0" java.lang.NegativeArraySizeException
at java.awt.image.DataBufferInt.<init>(Unknown Source)
at java.awt.image.Raster.createPackedRaster(Unknown Source)
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(Unknown Source)
at sun.awt.Win32GraphicsConfig.createCompatibleImage(Unknown Source)
at java.awt.GraphicsConfiguration.createCompatibleImage(Unknown Source)
at org.jgraph.JGraph.createBufferedImage(Unknown Source)
at org.jgraph.JGraph.getOffgraphics(Unknown Source)
at org.jgraph.plaf.basic.BasicGraphUI.paint(Unknown Source)
at javax.swing.plaf.ComponentUI.update(Unknown Source)
at javax.swing.JComponent.paintComponent(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JViewport.paint(Unknown Source)
at javax.swing.JComponent.paintChildren(Unknown Source)
at javax.swing.JComponent.paint(Unknown Source)
at javax.swing.JComponent.paintToOffscreen(Unknown Source)
at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
at javax.swing.RepaintManager.paint(Unknown Source)
at javax.swing.JComponent._paintImmediately(Unknown Source)
at javax.swing.JComponent.paintImmediately(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

si quelqu'un a deja rencontrer ce genre de probleme, qu'il me dise donc comment je commence à chercher l'erreur.
merci d'avance.