Bug on one specific case on multi-core

Sorry to bother you again, Axel, but I am just curious why actually the
version will make such a big difference? I have May 2011 as a single core
executable on my computer, it works for that input file, how come a more
recent version (Sep 2012) of multi-core cannot process that input file?

newer versions include new features, code improvements
and bugfixes. sometimes when a new feature is added, or
the code rearranged, new bugs are introduced as well.

on top of that, there also is the possibility, that some compilers
break code, i.e. the code is correct, but the compiler produces
an incorrectly working executable. sometimes also the opposite
happens, i.e. the code is not 100% correct, but the compiler still
produces a correct executable. or some compilers do and others
do not. finally, this can also be dependent on whether you run
in parallel or in serial or what operating system you run on.
with a large complex application with LAMMPS there are far too
many permutations of options and some of them happen extremely
rarely or are not at all anticipated when writing code.

in short, there can be many reasons why something doesn't work
in parallel but does in serial. hence the first step is always to
try and reproduce it with the latest version of the source code,
since that is the only version where somebody would be willing
to track a possible bug down and fix it.