diff -r 3c00e093bbe4 core.startup/src/org/netbeans/core/startup/layers/ParsingLayerCacheManager.java
--- a/core.startup/src/org/netbeans/core/startup/layers/ParsingLayerCacheManager.java	Mon Dec 17 15:43:27 2012 +0100
+++ b/core.startup/src/org/netbeans/core/startup/layers/ParsingLayerCacheManager.java	Mon Dec 17 16:46:18 2012 +0100
@@ -222,20 +222,21 @@
             fileOrFolder(qname, attrs);
         } else if (qname.equals("file")) {
             MemFileOrFolder mfof = fileOrFolder(qname, attrs);
-            if (!(mfof instanceof MemFile)) { // a collision between modules
-                throw new ClassCastException("mfof: " + mfof + " stack: " + curr); // NOI18N
+            if (!(mfof instanceof MemFile)) { 
+                // a collision between modules
+            } else {
+                buf.setLength(0);
+                ref = null;
+                String u = attrs.getValue("url");
+                if (u != null) {
+                    try {
+                        ref = new URL(base, u);
+                    } catch (MalformedURLException mfue) {
+                        throw (SAXException) new SAXException(mfue.toString()).initCause(mfue);
+                    }
+                }
+                weight = 0;
             }
-            buf.setLength(0);
-            ref = null;
-            String u = attrs.getValue("url");
-            if (u != null) {
-                try {
-                    ref = new URL(base, u);
-                } catch (MalformedURLException mfue) {
-                    throw (SAXException) new SAXException(mfue.toString()).initCause(mfue);
-                }
-            }
-            weight = 0;
         } else if (qname.equals("attr")) {
             attrCount++;
             MemAttr attr = new MemAttr();
@@ -341,8 +342,9 @@
     }
     
     public void endElement(String ns, String lname, String qname) throws SAXException {
-        if (qname.equals("file")) {
-            MemFile file = (MemFile) curr.peek();
+        Object poke;
+        if (qname.equals("file") && (poke = curr.peek()) instanceof MemFile) {
+            MemFile file = (MemFile) poke;
             if (weight /* #23609: reversed, so not > */>= file.weight) {
                 file.weight = weight;
                 file.contents = null;
diff -r 3c00e093bbe4 core.startup/test/unit/src/org/netbeans/core/startup/layers/CacheManagerTestBaseHid.java
--- a/core.startup/test/unit/src/org/netbeans/core/startup/layers/CacheManagerTestBaseHid.java	Mon Dec 17 15:43:27 2012 +0100
+++ b/core.startup/test/unit/src/org/netbeans/core/startup/layers/CacheManagerTestBaseHid.java	Mon Dec 17 16:46:18 2012 +0100
@@ -145,12 +145,12 @@
         List<URL> urls = Arrays.asList(
             loadResource("data/folder2.xml"),
             loadResource("data/folder1.xml"));
-        try {
-            FileSystem f = BinaryCacheManagerTest.store(m, urls);
-            fail("Should throw an exception");
-        } catch (IOException ex) {
-            // OK, collision
-        }
+        
+        FileSystem f = BinaryCacheManagerTest.store(m, urls);
+        final FileObject fld = f.findResource("folder");
+        
+        assertTrue("Is folder", fld.isFolder());
+        assertEquals("No content", 0, fld.getSize());
     }
     
     private void checkLastModified (FileSystem f, String file, String resource) throws Exception {
diff -r 3c00e093bbe4 o.n.bootstrap/test/unit/data/layers/data/folder2.xml
--- a/o.n.bootstrap/test/unit/data/layers/data/folder2.xml	Mon Dec 17 15:43:27 2012 +0100
+++ b/o.n.bootstrap/test/unit/data/layers/data/folder2.xml	Mon Dec 17 16:46:18 2012 +0100
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE filesystem PUBLIC "-//NetBeans//DTD Filesystem 1.2//EN" "http://www.netbeans.org/dtds/filesystem-1_2.dtd">
 <filesystem>
-    <file name="folder"/>
+    <file name="folder">NotEmpty</file>
 </filesystem>
\ No newline at end of file
diff -r 3c00e093bbe4 openide.filesystems/src/org/openide/filesystems/XMLFileSystem.java
--- a/openide.filesystems/src/org/openide/filesystems/XMLFileSystem.java	Mon Dec 17 15:43:27 2012 +0100
+++ b/openide.filesystems/src/org/openide/filesystems/XMLFileSystem.java	Mon Dec 17 16:46:18 2012 +0100
@@ -615,7 +615,7 @@
         private boolean isFolder;
         private String uri;
 
-        public ResourceElem(boolean isFolder, URL[] urlContext) {
+        public ResourceElem(boolean isFolder, URL... urlContext) {
             this.isFolder = isFolder;
             this.urlContext.addAll(Arrays.asList(urlContext));
 
@@ -625,19 +625,12 @@
             }
         }
 
-        public ResourceElem(boolean isFolder, URL urlContext) {
-            this.isFolder = isFolder;
-            this.urlContext.add(urlContext);
-
-            if (isFolder) {
+        ResourceElem addChild(String name, ResourceElem child) {
+            if (!isFolder) {
                 children = new ArrayList<ResourceElem>();
                 names = new ArrayList<String>();
-            }
-        }
-
-        ResourceElem addChild(String name, ResourceElem child) {
-            if (!isFolder) {
-                throw new IllegalArgumentException("not a folder"); // NOI18N
+                content = null;
+                isFolder = true;
             }
             assert name != null && name.indexOf("/") == -1:(child.isFolder ? "<folder name=":"<file name=")+name+" ...";//NOI18N
 
diff -r 3c00e093bbe4 openide.filesystems/test/unit/src/org/openide/filesystems/RepositoryTest.java
--- a/openide.filesystems/test/unit/src/org/openide/filesystems/RepositoryTest.java	Mon Dec 17 15:43:27 2012 +0100
+++ b/openide.filesystems/test/unit/src/org/openide/filesystems/RepositoryTest.java	Mon Dec 17 16:46:18 2012 +0100
@@ -56,6 +56,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Enumeration;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import org.netbeans.junit.NbTestCase;
@@ -96,7 +97,8 @@
         });
         FileObject r = FileUtil.getConfigRoot();
         assertTrue(r.isValid());
-        assertEquals(4, r.getChildren().length);  // org.openide.filesystems.resources.layer.xml, test-layer-1.xml, test-layer-2.xml, test/generated-layer.xml
+        List<FileObject> arr = Arrays.asList(r.getChildren());
+        assertEquals("Four " + arr, 4, arr.size());  // org.openide.filesystems.resources.layer.xml, test-layer-1.xml, test-layer-2.xml, test/generated-layer.xml
         assertNotNull(r.getFileObject("foo"));
         assertNotNull(r.getFileObject("bar"));
     }