LSF Server: could not load license

Hi All,
Please help me to solve the problem when i submit a job on the client:
#bsub -q normal -(blah blah....)
I got the error messages:
#batch system daemon not responding ... still trying
#batch system daemon not responding ... still trying
#batch system daemon not responding ... still trying
#batch system daemon not responding ... still trying
#batch system daemon not responding ... still trying
what is problem? how can I do to fix it?
Thanks