diff -r d884e5045327 autoupdate.services/src/org/netbeans/modules/autoupdate/services/OperationSupportImpl.java
--- a/autoupdate.services/src/org/netbeans/modules/autoupdate/services/OperationSupportImpl.java	Wed Oct 01 14:28:32 2008 +0200
+++ b/autoupdate.services/src/org/netbeans/modules/autoupdate/services/OperationSupportImpl.java	Tue Oct 07 16:00:21 2008 +0200
@@ -60,6 +60,8 @@
 import org.netbeans.spi.autoupdate.CustomInstaller;
 import org.openide.LifecycleManager;
 import org.openide.modules.ModuleInfo;
+import org.openide.util.Mutex.ExceptionAction;
+import org.openide.util.MutexException;
 
 /**
  * @author Jiri Rechtacek, Radek Matous
@@ -125,7 +127,7 @@
                     UpdateElementImpl impl = Trampoline.API.impl (operationInfo.getUpdateElement ());
                     moduleInfos.addAll (impl.getModuleInfos ());
                 }
-                Set<Module> modules = new HashSet<Module>();
+                final Set<Module> modules = new HashSet<Module>();
                 for (ModuleInfo info : moduleInfos) {
                     Module m = Utilities.toModule (info);
                     if (Utilities.canEnable (m)) {
@@ -137,7 +139,20 @@
                     }
                 }
                 assert mm != null;
-                enable(mm, modules);
+                final ModuleManager fmm = mm;
+                try {
+                    fmm.mutex ().writeAccess (new ExceptionAction () {
+                        public Object run () throws Exception {
+                            return enable(fmm, modules);
+                        }
+                    });
+                } catch (MutexException ex) {
+                    Exception x = ex.getException ();
+                    assert x instanceof OperationException : x + " is instanceof OperationException";
+                    if (x instanceof OperationException) {
+                        throw (OperationException) x;
+                    }
+                }
             } finally {
                 if (progress != null) {
                     progress.finish();