What does runuser: cannot set groups mean

I am installing nagios3 on centos.

After stopping the nagios server and then restarting I get the message

Starting nagios runuser: cannot set groups:Operation not permitted.

what does this mean

From serverfault Ric

• A few things off the top of my head. Does the group that belongs to the user your switching to exist? Does the runuser command have the setguid sticky bit set? Check the output of ls -l $(which runuser). Alternately, it's possible you might have a partition mounted with the nosuid flag. Check the output of mount for that.
  
  
  --Christopher Karel

  From Christopher Karel