[mpich-discuss] cannot execute binary file

Hi Guys, I just finished installing mpich. But when I tried to run it, it returned "cannot execute binary file". I double checked the file type by "file mpiexec.hydra", which got "mpiexec.hydra: ELF 64-bit LSB executable, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.16, not stripped". I am running 64-bit CentOS. Any ideas of this error? Thanks, YW