Try something for issue #1216

modules/WelcomeScreen/src/main/java/org/gephi/desktop/welcome/WelcomeAction.java

@@ -44,17 +44,25 @@ package org.gephi.desktop.welcome;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import javax.swing.JDialog;
+import javax.swing.SwingUtilities;
+import javax.swing.WindowConstants;
 import org.openide.windows.WindowManager;
 
 public final class WelcomeAction implements ActionListener {
 
     @Override
     public void actionPerformed(ActionEvent e) {
-        WelcomeTopComponent component = WelcomeTopComponent.getInstance();
-        JDialog dialog = new JDialog(WindowManager.getDefault().getMainWindow(),
-                component.getName(), false);
-        dialog.getContentPane().add(component);
-        dialog.setBounds(212, 237, 679, 378);
-        dialog.setVisible(true);
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                WelcomeTopComponent component = WelcomeTopComponent.getInstance();
+                JDialog dialog = new JDialog(WindowManager.getDefault().getMainWindow(),
+                        component.getName(), false);
+                dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
+                dialog.getContentPane().add(component);
+                dialog.setBounds(212, 237, 679, 378);
+                dialog.setVisible(true);
+            }
+        });
     }
 }

modules/WelcomeScreen/src/main/java/org/gephi/desktop/welcome/WelcomeTopComponent.java

@@ -47,12 +47,12 @@ import java.awt.event.ActionListener;
 import java.awt.event.ItemEvent;
 import java.awt.event.ItemListener;
 import java.io.File;
-import java.io.IOException;
 import java.io.InputStream;
 import javax.swing.AbstractAction;
 import javax.swing.Action;
 import javax.swing.JDialog;
 import javax.swing.JPanel;
+import javax.swing.SwingUtilities;
 import org.gephi.desktop.importer.api.ImportControllerUI;
 import org.gephi.desktop.mrufiles.api.MostRecentFiles;
 import org.gephi.desktop.project.api.ProjectControllerUI;
@@ -96,11 +96,16 @@ public final class WelcomeTopComponent extends JPanel {
     }
 
     private void closeDialog() {
-        Container container = this;
-        for (; !(container instanceof JDialog);) {
-            container = container.getParent();
-        }
-        container.setVisible(false);
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                Container container = WelcomeTopComponent.this;
+                for (; !(container instanceof JDialog);) {
+                    container = container.getParent();
+                }
+                container.setVisible(false);
+            }
+        });
     }
 
     private void initAction() {