I have a problema using APCUPSD
 

I'm installing APCUPSD in my network to monitor my UPS, but i'm having a little problem when i'm going to start it.
When i execute the command
"/sbin/apcupsd -f /etc/apcupsd/apcupsd.conf" to start, the Shell says this:

" apcupsd FATAL ERROR in apcserial.c at line 100
Unable to create serial port lock file "

I already checked the apcserial.c and the apcupsd.conf files but i can't
get the wrong line
I have an APC Smart-UPS

Can you please help me?
Thanks

P.D.: On what directory should I install the apcupd-3.8.6.tar.gz file?