If one simply comment out the instantiation - or declaration - (and
"addManager")  of the MuPairProduction process, for mu+ and/or mu-, in the
example N02, then one gets a core dump because the energy loss table are lost.

Modified segment of : ExN02PhysicsList.cc :

   } else if( particleName == "mu+" ||
               particleName == "mu-"    ) {
    //muon
     // Construct processes for muon+
     G4VProcess* aMultipleScattering = new G4MultipleScattering();
     G4VProcess* aBremsstrahlung = new G4MuBremsstrahlung();
//     G4VProcess* aPairProduction = new G4MuPairProduction();
     G4VProcess* anIonisation = new G4MuIonisation();
      // add processes
     pmanager->AddProcess(anIonisation);
     pmanager->AddProcess(aMultipleScattering);
     pmanager->AddProcess(aBremsstrahlung);
//     pmanager->AddProcess(aPairProduction);
      // set ordering for AlongStepDoIt
      pmanager->SetProcessOrdering(aMultipleScattering, idxAlongStep,  1);
      pmanager->SetProcessOrdering(anIonisation, idxAlongStep,  2);
      // set ordering for PostStepDoIt
      pmanager->SetProcessOrdering(aMultipleScattering, idxPostStep, 1);
      pmanager->SetProcessOrdering(anIonisation, idxPostStep, 2);
      pmanager->SetProcessOrdering(aBremsstrahlung, idxPostStep, 3);
//      pmanager->SetProcessOrdering(aPairProduction, idxPostStep, 4);

	when shooting muons of ~130 MeV gives:

*********************************************************************************************************
* G4Track Information:   Particle = mu+,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng
NextVolu   Process
    0   -2.5 cm     0 fm     0 fm   131 MeV     0 eV     0 fm     0
fmTargetPV            initStep

Program received signal SIGSEGV, Segmentation fault.
G4RWTPtrOrderedVector<G4PhysicsVector>::operator() (this=0x0, i=1)
    at
/local/data01/lebrun/geant4/geant4.2.0/source/global/STLInterface/g4rw/tpordvec.icc:47
47        if(rwsize<=i && i<std_pvector::size())
(gdb) quit

	(gdb) where
#0  G4RWTPtrOrderedVector<G4PhysicsVector>::operator() (this=0x0, i=1)
    at
/local/data01/lebrun/geant4/geant4.2.0/source/global/STLInterface/g4rw/tpordvec.icc:47
#1  0x80ac0b0 in G4VMuEnergyLoss::GetConstraints (this=0x84c5790,
aParticle=0x8443108,
    aMaterial=0x84935b8) at src/G4VMuEnergyLoss.cc:352
#2  0x80ac69e in G4VMuEnergyLoss::GetContinuousStepLimit (this=0x84c5790,
track=@0x8443938,
    currentMinimumStep=6.4237754657120725) at include/G4VMuEnergyLoss.icc:35
#3  0x812561a in
G4VContinuousDiscreteProcess::AlongStepGetPhysicalInteractionLength ()
    at
/local/data01/lebrun/geant4/geant4.2.0/source/geometry/management/include/G4LogicalVolume.hh:205
#4  0x807f8c2 in G4SteppingManager::Stepping () at src/ExN02TrackerHit.cc:19
#5  0x8077842 in G4TrackingManager::ProcessOneTrack () at
src/ExN02TrackerHit.cc:19
#6  0x8065d44 in G4EventManager::ProcessOneEvent () at src/ExN02TrackerHit.cc:19
#7  0x805264b in G4RunManager::DoEventLoop () at src/ExN02TrackerHit.cc:19
#8  0x805214e in G4RunManager::BeamOn () at src/ExN02TrackerHit.cc:19
#9  0x805b6ab in G4RunMessenger::SetNewValue () at src/ExN02TrackerHit.cc:19

.....

I found this feature running an other example of mine, so it is not peculiar to
ExN02.  I also think this is a feature of 4.2.0, I was able to run without
muon induced pair production in 4.1.1.

						Paul.