the proper time goes back

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Hello,

I am trying to put an Electromagnetic field (in a localized volume) after an Tungsten target. I have followed the recommendation gave by Peter Gumplinger http://tinyurl.com/nfpk7t So inside my DetectorConstruction I have

    G4ThreeVector positionTarget= G4ThreeVector(0,0,samplerLength+targetSizeZ/2);
    G4Box* solidTarget = new G4Box("Target",targetSizeXY/2.,targetSizeXY/2.,targetSizeZ/2.);
    G4LogicalVolume* logicTarget = new G4LogicalVolume(solidTarget, aMaterial,"Target");
    pTarget = new G4PVPlacement(0,positionTarget,logicTarget,"Target",lWorld,false,0);
    G4VisAttributes* LogVisAttTarget= new G4VisAttributes(G4Colour(.0,1.,0.));
    logicTarget ->SetVisAttributes(LogVisAttTarget);
    // register logical Volume in PolarizationManager with zero polarization
    G4PolarizationManager * polMgr = G4PolarizationManager::GetInstance();
    polMgr->SetVolumePolarization(logicTarget,G4ThreeVector(0.,0.,0.));

    //Target Calo
    PPSTargetCaloSD* TargetCaloSD= new PPSTargetCaloSD("TargetCaloSD",this);
    SDman->AddNewDetector(TargetCaloSD);
    logicTarget->SetSensitiveDetector(TargetCaloSD);

 static G4bool fieldIsInitialized = false;

    if(!fieldIsInitialized)

    {
        Field = new PPSField();
        pEquation = new G4EqMagElectricField(Field);
        pStepper = new G4ClassicalRK4 (pEquation);
        pFieldMgr = new G4FieldManager();
        //pFieldMgr = G4TransportationManager::GetTransportationManager()->GetFieldManager();
        pIntgrDriver = new G4MagInt_Driver(0.000001*mm,pStepper,pStepper->GetNumberOfVariables() );
        pChordFinder = new G4ChordFinder(pIntgrDriver);
        pFieldMgr->SetChordFinder( pChordFinder );
        pFieldMgr->SetDetectorField(Field);
        fieldIsInitialized = true;
    }

    G4ThreeVector positionCapture= G4ThreeVector(0,0,targetSizeZ+CaptureLength/2.);
    G4Box *solidCapture = new G4Box("CaptureBox",AMD_XY_size,AMD_XY_size,CaptureLength/2);
    G4LogicalVolume* logicCapture = new G4LogicalVolume(solidCapture,Vacuum,"theCaptureBox");
    pCapture=new G4PVPlacement(0,positionCapture,logicCapture,"CaptureBox",lWorld,false,0);
    G4VisAttributes* LogVisAttCapture= new G4VisAttributes(G4Colour(1.0,0.5,0.5));
    logicCapture ->SetVisAttributes(LogVisAttCapture);
    logicCapture->SetFieldManager(pFieldMgr,true);

And my PPSField class is only:

PPSField::PPSField() 
{     }
void PPSField::GetFieldValue(const double point[4], double *Bfield ) const
{ 
	// Magnetic field
	Bfield[0] = 0;
	Bfield[1] = 0;
	Bfield[2] = 0.5*tesla;

	// Electric field
	Bfield[3] = 0;
	Bfield[4] = 0;
	Bfield[5] = 17.*megavolt/m;

}

When I run a electron beam of Several MeV impinging on my target I have those following error:

G4ParticleChange::CheckIt    : the global time goes back  !!
  Difference:  0.074773488261472[ns] 
  G4ParticleChange::CheckIt    : the proper time goes back  !!
  Difference:  0.0026325540767444[ns] 
 G4ParticleChange::CheckIt 
      -----------------------------------------------
        G4ParticleChange Information  
      -----------------------------------------------
        # of 2ndaries       :                    0
      -----------------------------------------------
        Energy Deposit (MeV):                    0
        Non-ionizing Energy Deposit (MeV):                    0
        Track Status        :                Alive
        True Path Length (mm) :                 11.1
        Stepping Control      :                    0
        Mass (GeV)   :                    0
        Charge (eplus)   :                    0
        MagneticMoment   :                    0
                :  =                    0*[e hbar]/[2 m]
        Position - x (mm)   :                   -9
        Position - y (mm)   :                -2.96
        Position - z (mm)   :                 14.9
        Time (ns)           :                    0
        Proper Time (ns)    :             -0.00249
        Momentum Direct - x :               -0.795
        Momentum Direct - y :                -0.55
        Momentum Direct - z :                0.255
        Kinetic Energy (MeV):                   14
        Polarization - x    :                    0
        Polarization - y    :                    0
        Polarization - z    :                    0
        Touchable (pointer) :            0x4dbd0a0

Do you have an idea of what I am doing wrong ? by advance thank you Olivier