Index: trunk/src/org/openstreetmap/josm/command/MoveCommand.java
===================================================================
--- trunk/src/org/openstreetmap/josm/command/MoveCommand.java	(revision 3252)
+++ trunk/src/org/openstreetmap/josm/command/MoveCommand.java	(revision 3253)
@@ -95,5 +95,5 @@
                 throw new AssertionError("null detected in node list");
             if (n.getEastNorth() == null)
-                throw new AssertionError("unexpected null value for n.getEastNorth(). id of n is " + n.getUniqueId());
+                throw new AssertionError(n.get3892DebugInfo());
 
             n.setEastNorth(n.getEastNorth().add(x, y));
Index: trunk/src/org/openstreetmap/josm/data/coor/CachedLatLon.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/coor/CachedLatLon.java	(revision 3252)
+++ trunk/src/org/openstreetmap/josm/data/coor/CachedLatLon.java	(revision 3253)
@@ -47,3 +47,8 @@
         return "CachedLatLon[lat="+lat()+",lon="+lon()+"]";
     }
+
+    // Only for Node.get3892DebugInfo()
+    public Projection getProjection() {
+        return proj;
+    }
 }
Index: trunk/src/org/openstreetmap/josm/data/osm/Node.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/Node.java	(revision 3252)
+++ trunk/src/org/openstreetmap/josm/data/osm/Node.java	(revision 3253)
@@ -198,3 +198,19 @@
         return (OsmPrimitive.getFilteredList(getReferrers(), Way.class)).size() > 1;
     }
+
+    public String get3892DebugInfo() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Unexpected error. Please report it to http://josm.openstreetmap.de/ticket/3892\n");
+        builder.append(toString());
+        builder.append("\n");
+        if (coor == null) {
+            builder.append("Coor is null\n");
+        } else {
+            builder.append(String.format("EastNorth: %s\n", coor.getEastNorth()));
+            builder.append(coor.getProjection());
+            builder.append("\n");
+        }
+
+        return builder.toString();
+    }
 }