Index: src/wmsplugin/WMSLayer.java
===================================================================
--- src/wmsplugin/WMSLayer.java	(revision 13778)
+++ src/wmsplugin/WMSLayer.java	(working copy)
@@ -62,7 +62,7 @@
     protected String baseURL;
     protected final int serializeFormatVersion = 4;
 
-    private ExecutorService executor;
+    private ExecutorService executor = null;
 
     public WMSLayer() {
         this(tr("Blank Layer"), null);
@@ -82,6 +82,13 @@
         
         executor = Executors.newFixedThreadPool(3);
     }
+    
+    public void destroy() {
+        try { 
+            executor.shutdown();  
+        // Might not be initalized, so catch NullPointer as well
+        } catch(Exception x) {}
+    }
 
     public void getPPD(){
         pixelPerDegree = mv.getWidth() / (bounds().max.lon() - bounds().min.lon());