diff -r ab16ccd545a5 masterfs/src/org/netbeans/modules/masterfs/filebasedfs/fileobjects/FileObj.java
--- a/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/fileobjects/FileObj.java	Wed Jan 18 05:25:23 2012 +0100
+++ b/masterfs/src/org/netbeans/modules/masterfs/filebasedfs/fileobjects/FileObj.java	Wed Jan 18 18:17:06 2012 +0100
@@ -55,6 +55,7 @@
 import java.util.Enumeration;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import javax.swing.SwingUtilities;
 import org.netbeans.modules.masterfs.filebasedfs.naming.FileNaming;
 import org.netbeans.modules.masterfs.filebasedfs.utils.FSException;
 import org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager;
@@ -152,6 +153,9 @@
             FSException.annotateException(fex);            
             throw fex;
         }
+        if (Boolean.getBoolean("perf.IOAWT") && SwingUtilities.isEventDispatchThread()) {
+            Exceptions.printStackTrace(new IllegalStateException("getOutputStream invoked in AWT")); // NOI18N
+        }
         return retVal;
     }
 
@@ -211,6 +215,9 @@
             throw fex;
         }
         assert inputStream != null;
+        if (Boolean.getBoolean("perf.IOAWT") && SwingUtilities.isEventDispatchThread()) {
+            Exceptions.printStackTrace(new IllegalStateException("getInputStream invoked in AWT")); // NOI18N
+        }
         return inputStream;
     }
 
diff -r ab16ccd545a5 o.n.bootstrap/src/org/netbeans/TopSecurityManager.java
--- a/o.n.bootstrap/src/org/netbeans/TopSecurityManager.java	Wed Jan 18 05:25:23 2012 +0100
+++ b/o.n.bootstrap/src/org/netbeans/TopSecurityManager.java	Wed Jan 18 18:17:06 2012 +0100
@@ -65,7 +65,9 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.logging.LoggingPermission;
+import javax.swing.SwingUtilities;
 import org.openide.modules.Places;
+import org.openide.util.Exceptions;
 import org.openide.util.Lookup;
 
 /** NetBeans security manager implementation.
@@ -358,7 +360,9 @@
         if (! check) {
             return;
         }
-        
+        if (Boolean.getBoolean("perf.IOAWT") && SwingUtilities.isEventDispatchThread()) {
+            Exceptions.printStackTrace(new IllegalStateException("Network call invoked in AWT")); // NOI18N
+        }        
         try {
             checkPermission(allPermission);
             return;
@@ -400,6 +404,11 @@
 
     public @Override void checkPermission(Permission perm) {
 //        assert checkLogger(perm); //#178013 & JDK bug 1694855
+        if (Boolean.getBoolean("perf.IOAWT")) {
+            if (perm instanceof java.net.SocketPermission && SwingUtilities.isEventDispatchThread()) {
+                Exceptions.printStackTrace(new IllegalStateException("Network call invoked in AWT")); // NOI18N
+            }
+        }
         checkSetSecurityManager(perm);
         
         //