Index: src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/CacheReference.java
===================================================================
RCS file: /cvs/mdr/src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/CacheReference.java,v
retrieving revision 1.2
diff -d -u -b -B -r1.2 CacheReference.java
--- src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/CacheReference.java	7 Feb 2002 10:00:36 -0000	1.2
+++ src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/CacheReference.java	4 Mar 2002 07:47:56 -0000
@@ -83,6 +83,7 @@
      */
     public void clear() {
         weaken();
+        key = null;
         super.clear();
     }
     
Index: src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/MDRCache.java
===================================================================
RCS file: /cvs/mdr/src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/MDRCache.java,v
retrieving revision 1.2
diff -d -u -b -B -r1.2 MDRCache.java
--- src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/MDRCache.java	7 Feb 2002 10:00:36 -0000	1.2
+++ src/org/netbeans/mdr/persistence/btreeimpl/btreestorage/MDRCache.java	4 Mar 2002 07:47:56 -0000
@@ -246,7 +246,13 @@
         CacheReference cr;
         while ((cr = (CacheReference)queue.poll()) != null) {
             //if (cr.inCache) {
-            i += hashOnId.remove(cr.getKey()) == null ? 0 : 1;
+            Object k = cr.getKey();
+            if (k == null)
+                // the reference was already replaced by another one.
+                continue;
+            
+            CacheReference cr2 = (CacheReference)hashOnId.remove(k);
+            i += cr2 == null ? 0 : 1;
             // cr.inCache = false;
             //}
         }