check you nagios.log (last 4 hours) for some unexpected entries
root@checkmk:~# omd su YOURSITE
OMD[YOURSITE]:~$ cd ~/var/nagios
OMD[YOURSITE]:~/var/nagios$ cat nagios.log
check you nagios.log (last 4 hours) for some unexpected entries
root@checkmk:~# omd su YOURSITE
OMD[YOURSITE]:~$ cd ~/var/nagios
OMD[YOURSITE]:~/var/nagios$ cat nagios.log