Out NetBeans Platform Based application relies intensively on ANT Tasks. 
Sometimes thie exception occurs: 
java.lang.ArrayIndexOutOfBoundsException: 1 >= 1
	at java.util.Vector.elementAt(Vector.java:427)
	at javax.swing.DefaultListModel.getElementAt(DefaultListModel.java:70)
	at org.netbeans.modules.progress.spi.TaskModel.getSelectedHandle(TaskModel.java:154)
	at org.netbeans.modules.progress.spi.TaskModel.updateSelection(TaskModel.java:91)
	at org.netbeans.modules.progress.spi.Controller.toIndeterminate(Controller.java:158)
	at org.netbeans.modules.progress.spi.InternalHandle.toIndeterminate(InternalHandle.java:182)
	at org.netbeans.api.progress.ProgressHandle.switchToIndeterminate(ProgressHandle.java:106)
	at org.apache.tools.ant.module.bridge.impl.NbBuildLogger.checkForStop(NbBuildLogger.java:204)
	at org.apache.tools.ant.module.bridge.impl.NbBuildLogger.messageLogged(NbBuildLogger.java:583)
	at org.apache.tools.ant.Project.fireMessageLoggedEvent(Project.java:2254)
	at org.apache.tools.ant.Project.fireMessageLogged(Project.java:2290)
	at org.apache.tools.ant.Project.log(Project.java:470)
	at org.apache.tools.ant.Project.log(Project.java:459)
	at org.apache.tools.ant.PropertyHelper.setNewProperty(PropertyHelper.java:708)
	at org.apache.tools.ant.Project.setNewProperty(Project.java:553)
	at org.apache.tools.ant.taskdefs.Ant.addAlmostAll(Ant.java:646)
	at org.apache.tools.ant.taskdefs.Ant.initializeProject(Ant.java:232)
	at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:345)
	at org.apache.tools.ant.taskdefs.CallTarget.execute(CallTarget.java:105)
	at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
	at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
	at org.apache.tools.ant.Task.perform(Task.java:348)
	at org.apache.tools.ant.Target.execute(Target.java:390)
	at org.apache.tools.ant.Target.performTasks(Target.java:411)
	at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
	at org.apache.tools.ant.helper.SingleCheckExecutor.executeTargets(SingleCheckExecutor.java:38)
	at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
	at com.streamsim.hmscript.myant.MyBaseAntTask.execute(MyBaseAntTask.java:381)


this is why we call a task from within  a task.
This is the code of execute() in MyBaseAntTask that causes the problem
if (locals.size() > 0 && !(locals.size() == 1 && "".equals(locals.get(0)))) {
                Throwable t = null;
                try {
                    log("Entering " + antFile + "...", Project.MSG_VERBOSE);
                    newProject.fireSubBuildStarted();
                    newProject.executeTargets(locals);
                } catch (BuildException ex) {
                    t = ProjectHelper.addLocationToBuildException(ex, getLocation());
                    throw (BuildException) t;
                } finally {
                    log("Exiting " + antFile + '.', Project.MSG_VERBOSE);
                    newProject.fireSubBuildFinished(t);
                }
            }