// here's the binding code
dbc = new DataBindingContext();
IObservableValue ovView = SWTObservables.observeText(filePath_txt,
					SWT.Modify);
IObservableValue ovModel = BeansObservables.observeValue(
					getModel(), "filePath");

UpdateValueStrategy strategy = getUpdateValueStrategy();
binding = dbc.bindValue(ovView, ovModel, strategy, null);
WizardPageSupport wps = WizardPageSupport.create(this, dbc);
....
// get the strategy
private UpdateValueStrategy getUpdateValueStrategy() {
			return new UpdateValueStrategy(UpdateValueStrategy.POLICY_UPDATE)
					.setBeforeSetValidator(new FileValidator());
}

class FileValidator implements IValidator {
...
// roughly speaking, it validates whether the file path entered in filePath_txt control is right, and this part of code works properly
@Override
public IStatus validate(Object value) {
...
}
}

// before the fix
private void reset() {
	getModel().setFilePath(null);
	dbc.updateTargets();
	dbc.removeBinding(binding);
	doBinding();       // creating the dbc
}

// after the fix, appears that I just have to reset the model value and call dbc.updateTargets() in order to reset the wizard validation state
private void reset() {
	getModel().setFilePath(null);
	dbc.updateTargets();
	// dbc.removeBinding(binding);
	// dbc.addBinding(binding);
        // doBinding();       // creating the dbc
}

private void reset() {
	getModel().setFilePath(null);   //reset model value
	binding.init(dbc);  // reset validation status
	wps.dispose();  // recreate the wizard page support with dbc
	wps = WizardPageSupport.create(BatchFileSelectionPage.this, dbc);
}