pythia8 return code

Hi all,
I'm having some issues with Madgraph and Pythia
when i opened the mg5 and start to type:
  generate e+ e- > k+ k-
  add process e+ e- > k+ k- g
k is defined by myself conclude u d s c b

when i start to launch,the bug comes out:

INFO: Running Pythia8 [arXiv:1410.3012]
No user-defined value for Pythia8 parameter 'JetMatching:nJetMax'. Setting it automatically to 1.
Follow Pythia8 shower by running the following command (in a separate terminal):
    tail -f /home/surrutia/madgraph/signal_e-e-2j/Events/run_01/tag_1_pythia8.log
Command "generate_events run_01" interrupted with error:
InvalidCmd : Pythia8 shower interrupted with return code 139.
        You can find more information in this log file:
        /home/download/madgraph/a23p/Events/run_01/tag_1_pythia8.log

In the mentioned log file, I found the following message:

/home/surrutia/madgraph/signal_e-e-2j/Events/run_01/run_shower.sh: line 2: 29494 Segmentation fault (core dumped) LD_LIBRARY_PATH=/home/surrutia/madgraph/HEPTools/MG5aMC_PY8_interface/MG5aMC_PY8_interface tag_1_pythia8.cmd

i don't know where the problem is , it's OK when i generate e+ e-> k+ k- or generate e+ e->k+ k- g
but when i used the "add process",the problem comes.

Thanks,
Vickers