Index: src/org/aspectj/weaver/loadtime/Aj.java
===================================================================
RCS file: /home/technology/org.aspectj/modules/loadtime/src/org/aspectj/weaver/loadtime/Aj.java,v
retrieving revision 1.15
diff -u -r1.15 Aj.java
--- src/org/aspectj/weaver/loadtime/Aj.java	13 Dec 2005 22:23:24 -0000	1.15
+++ src/org/aspectj/weaver/loadtime/Aj.java	4 Jan 2006 07:52:11 -0000
@@ -52,8 +52,8 @@
      */
     public byte[] preProcess(String className, byte[] bytes, ClassLoader loader) {
         //TODO AV needs to doc that
-        if (loader == null || className == null) {
-            // skip boot loader or null classes (hibernate)
+        if (loader == null || className == null || className.startsWith("org/aspectj/")) {
+            // skip boot loader, null classes (hibernate), and any AspectJ implementation classes (if weaving into aspectjweaver.jar) 
             return bytes;
         }
 
@@ -117,21 +117,30 @@
 
     static class ExplicitlyInitializedClassLoaderWeavingAdaptor {
         private final ClassLoaderWeavingAdaptor weavingAdaptor;
-        private boolean isInitialized;
+        private final static int NOT_INITIALIZED = 0;
+        private final static int IS_INITIALIZING = 1;
+        private final static int FINISHED_INITIALIZING = 2;
+        private int initializationState;
 
         public ExplicitlyInitializedClassLoaderWeavingAdaptor(ClassLoaderWeavingAdaptor weavingAdaptor) {
             this.weavingAdaptor = weavingAdaptor;
-            this.isInitialized = false;
+            this.initializationState = NOT_INITIALIZED;
         }
 
         private void initialize(ClassLoader loader, IWeavingContext weavingContext) {
-            if (!isInitialized) {
-                isInitialized = true;
+        	//thread safety?
+            if (initializationState == NOT_INITIALIZED) {
+            	initializationState = IS_INITIALIZING;
                 weavingAdaptor.initialize(loader, weavingContext);
+            	initializationState = FINISHED_INITIALIZING;
             }
         }
-
+        
         public ClassLoaderWeavingAdaptor getWeavingAdaptor(ClassLoader loader, IWeavingContext weavingContext) {
+            if (initializationState == IS_INITIALIZING) {
+            	// can't weave myself while initializing: the null return causes the system to return unwoven bytes 
+            	return null;
+            }
             initialize(loader, weavingContext);
             return weavingAdaptor;
         }