Ubuntu/Arduino error

Experimental:  JNI_OnLoad called.
Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version   = RXTX-2.1-7
Exception in thread "Thread-1" java.lang.NullPointerException
	at sun.awt.X11.GtkFileDialogPeer.setFileInternal(GtkFileDialogPeer.java:79)
	at sun.awt.X11.GtkFileDialogPeer.run(Native Method)
	at sun.awt.X11.GtkFileDialogPeer.showNativeDialog(GtkFileDialogPeer.java:172)
	at sun.awt.X11.GtkFileDialogPeer.access$000(GtkFileDialogPeer.java:39)
	at sun.awt.X11.GtkFileDialogPeer$1.run(GtkFileDialogPeer.java:114)