Index: /trunk/src/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerAction.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerAction.java	(revision 11077)
+++ /trunk/src/org/openstreetmap/josm/gui/dialogs/layer/DeleteLayerAction.java	(revision 11078)
@@ -47,5 +47,9 @@
             return;
         for (Layer l: selectedLayers) {
-            Main.getLayerManager().removeLayer(l);
+            if (model.getLayerManager().containsLayer(l)) {
+                // it may happen that this call removes other layers.
+                // this is why we need to check if every layer is still in the list of selected layers.
+                model.getLayerManager().removeLayer(l);
+            }
         }
     }