diff -r 4e52836d327b masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/FileName.java
--- a/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/FileName.java	Tue May 18 14:58:39 2010 +0200
+++ b/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/FileName.java	Fri Jun 04 11:45:33 2010 +0200
@@ -58,6 +58,7 @@
     private CharSequence name;
     private final FileNaming parent;
     private Integer id;
+    Object status;
 
     protected FileName(final FileNaming parent, final File file) {
         this.parent = parent;
diff -r 4e52836d327b masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/NamingFactory.java
--- a/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/NamingFactory.java	Tue May 18 14:58:39 2010 +0200
+++ b/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/naming/NamingFactory.java	Fri Jun 04 11:45:33 2010 +0200
@@ -49,6 +49,7 @@
 import java.lang.ref.Reference;
 import java.lang.ref.WeakReference;
 import java.util.*;
+import java.util.logging.Logger;
 import org.netbeans.modules.masterfs.providers.ProvidedExtensions;
 
 /**
@@ -56,6 +57,7 @@
  */
 public final class NamingFactory {
     private static final Map nameMap = new WeakHashMap();
+    private static final Logger LOG = Logger.getLogger(NamingFactory.class.getName());
 
     public static synchronized FileNaming fromFile(final File file) {
         final LinkedList<File> list = new LinkedList<File>();
@@ -233,36 +235,56 @@
 
     private static List collectChildren(FileName parent) {
         assert Thread.holdsLock(NamingFactory.class);
+        long now = System.currentTimeMillis();
         List retval = new ArrayList();
+        Object isChild = new Object();
+        Object isNotChild = new Object();
         for (Object value : nameMap.values()) {
             if (value instanceof List) {
                 for (Object item : (List) value) {
                     Reference ref = (Reference) item;
-                    FileNaming naming = (FileNaming) ref.get();
-                    if (isChild(parent, naming)) {
+                    FileName naming = (FileName) ref.get();
+                    if (isChild(parent, naming, isChild, isNotChild)) {
                         retval.add(naming);
                     }
                 }
             } else {
                 Reference ref = (Reference) value;
-                FileNaming naming = (FileNaming) ref.get();
-                if (isChild(parent, naming)) {
+                FileName naming = (FileName) ref.get();
+                if (isChild(parent, naming, isChild, isNotChild)) {
                     retval.add(naming);
                 }
             }
         }
+        LOG.info(retval.size() + " children for " + parent + " took " + (System.currentTimeMillis() - now + " all names: " + nameMap.size()));
         return retval;
     }
     
-    private static boolean isChild(FileName parent, FileNaming naming) {
-        FileNaming temp = naming;
+    private static boolean isChild(
+        FileName parent, FileName naming, Object isChild, Object isNotChild
+    ) {
+        FileName temp = naming;
+        boolean found = false;
         while (temp != null) {
             if (temp == parent) {
-                return true;
+                found = true;
+                break;
             }
-            temp = temp.getParent();
+            if (temp.status == isChild) {
+                found = true;
+                break;
+            }
+            if (temp.status == isNotChild) {
+                break;
+            }
+            temp = (FileName)temp.getParent();
         }
-        return false;
+        FileName again = naming;
+        while (again != temp) {
+            again.status = found ? isChild : isNotChild;
+            again = (FileName)again.getParent();
+        }
+        return found;
     }
     
     private static Reference getReference(final List list, final File f) {