I do apologise. I had used Puppet to distribute the config files to my nodes, and I made a copy-paste error. Both mmm_common.conf and mmm_mon.conf contained the contents of mmm_mon.conf. No surprise it didn't start. I've now fixed that, and the daemon starts.
However, I still think the error message I was given isn't too helpful. Most other daemons will give a specific error and tell you which config file and which line number are causing the error.
I do apologise. I had used Puppet to distribute the config files to my nodes, and I made a copy-paste error. Both mmm_common.conf and mmm_mon.conf contained the contents of mmm_mon.conf. No surprise it didn't start. I've now fixed that, and the daemon starts.
However, I still think the error message I was given isn't too helpful. Most other daemons will give a specific error and tell you which config file and which line number are causing the error.