Index: trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java	(revision 18937)
+++ trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java	(revision 18938)
@@ -151,5 +151,7 @@
                     map.removeToggleDialog(dialog);
                 }
-                dialog.destroy();
+                if (!dialog.isDestroyed()) {
+                    dialog.destroy();
+                }
             }
         }
@@ -424,4 +426,10 @@
         cancelLoadingImage();
         super.destroy();
+        // Ensure that this dialog is removed from memory
+        destroyInstance();
+    }
+
+    private boolean isDestroyed() {
+        return dialogsPanel == null;
     }