diff --git a/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformProject.java b/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformProject.java
--- a/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformProject.java
+++ b/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformProject.java
@@ -64,7 +64,6 @@
 import org.openide.util.ImageUtilities;
 import org.openide.util.Lookup;
 import org.openide.util.Mutex;
-import org.openide.util.Utilities;
 import org.openide.util.lookup.Lookups;
 import org.w3c.dom.Element;
 import org.w3c.dom.NodeList;
@@ -111,10 +110,11 @@
         aux = helper().createAuxiliaryConfiguration(); // AuxiliaryConfiguration
         FreeformFileEncodingQueryImpl FEQImpl = new FreeformFileEncodingQueryImpl(helper(), evaluator());
         helper().addAntProjectListener(FEQImpl);
+        FreeformSources sources = new FreeformSources(this);
         Lookup baseLookup = Lookups.fixed(
             this,
             new Info(), // ProjectInformation
-            new FreeformSources(this), // Sources
+            sources, // Sources
             new Actions(this), // ActionProvider
             new View(this), // LogicalViewProvider
             new ProjectCustomizerProvider(this), // CustomizerProvider
@@ -125,6 +125,7 @@
             new LookupMergerImpl(), // LookupMerger or ActionProvider
             UILookupMergerSupport.createPrivilegedTemplatesMerger(),
             UILookupMergerSupport.createRecommendedTemplatesMerger(),
+            UILookupMergerSupport.createProjectOpenHookMerger(sources),
             new FreeformProjectOperations(this),
 	    new FreeformSharabilityQuery(helper()), //SharabilityQueryImplementation
             Accessor.DEFAULT.createProjectAccessor(this), //Access to AntProjectHelper and PropertyEvaluator
diff --git a/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformSources.java b/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformSources.java
--- a/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformSources.java
+++ b/ant.freeform/src/org/netbeans/modules/ant/freeform/FreeformSources.java
@@ -50,6 +50,7 @@
 import org.netbeans.spi.project.support.ant.AntProjectEvent;
 import org.netbeans.spi.project.support.ant.AntProjectListener;
 import org.netbeans.spi.project.support.ant.SourcesHelper;
+import org.netbeans.spi.project.ui.ProjectOpenedHook;
 import org.openide.util.ChangeSupport;
 import org.openide.util.Mutex;
 import org.w3c.dom.Element;
@@ -59,14 +60,14 @@
  * XXX will not correctly unregister released external source roots
  * @author Jesse Glick
  */
-final class FreeformSources implements Sources, AntProjectListener {
+final class FreeformSources extends ProjectOpenedHook implements Sources, AntProjectListener {
     
     private final FreeformProject project;
+    private SourcesHelper h;
     
     public FreeformSources(FreeformProject project) {
         this.project = project;
         project.helper().addAntProjectListener(this);
-        initSources(); // have to register external build roots eagerly
     }
     
     private Sources delegate;
@@ -84,7 +85,7 @@
     }
     
     private Sources initSources() {
-        final SourcesHelper h = new SourcesHelper(project.helper(), project.evaluator());
+        h = new SourcesHelper(project.helper(), project.evaluator());
         Element genldata = project.getPrimaryConfigurationData();
         Element foldersE = Util.findElement(genldata, "folders", FreeformProjectType.NS_GENERAL); // NOI18N
         if (foldersE != null) {
@@ -119,11 +120,6 @@
                 }
             }
         }
-        ProjectManager.mutex().postWriteRequest(new Runnable() {
-            public void run() {
-                h.registerExternalRoots(FileOwnerQuery.EXTERNAL_ALGORITHM_TRANSIENT);
-            }
-        });
         return h.createSources();
     }
     
@@ -143,5 +139,12 @@
     public void propertiesChanged(AntProjectEvent ev) {
         // ignore
     }
+
+    protected void projectOpened() {
+        getSourceGroups(TYPE_GENERIC);
+        h.registerExternalRoots(FileOwnerQuery.EXTERNAL_ALGORITHM_TRANSIENT);
+    }
+
+    protected void projectClosed() {}
     
 }