Fatal X11 error (connection to server lost?!) using screen


I was running a long job using screen command in the terminal at home. When I logout the lxplus6, my job directly crashed with errors:
Error in TFile::TFile: no read permission, could not open file /afs/cern.ch/user/h/hluo/BRfit/2014/tools/final/normalize_integrate_barrier_no.root
Root > Function mass_only() busy flag cleared
Error in : fatal X11 error (connection to server lost?!)

If I run the job on a desktop and do not logout the lxpus6, the job can run correctly. When the platform was lxplus5, I also do not encounter this problem. My linux version is:
Linux version 2.6.32-431.29.2.el6.x86_64 (mockbuild@c6b9.bsys.dev.centos.org) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-4) (GCC) )
and the root version in .bashrc is:
. /afs/cern.ch/sw/lcg/contrib/gcc/4.8.1/x86_64-slc6/setup.sh
. /afs/cern.ch/sw/lcg/app/releases/ROOT/5.34.21/x86_64-slc6-gcc48-opt/root/bin/thisroot.sh

The cause seems to be that the connection is lost when I logout lxplus6, but I do know what happened to the new platform.

It looks like your cession was too long and you were disconnected somehow … may be ask the lxplus people ?