Munin Plugin - NTP kernel PLL estimated error

Does anyone know what the graph NTP kernel PLL estimated error (secs) in Munin Represents? From the title I can asses that it is estimating the number of errors per second in NTP kernel phase-locked loop but does anyone have anymore information then that and possibly if and where these errors are logged? These errors have been coming up almost every day at 2am and it has a bad habit of crashing my server. Any help on this would be greatly appreciated.

I am using Munin version 1.4.5
WHM 11.30.3 (build 5)
CENTOS 5.7 x86_64 standard

 

I figured out what was causing it but not really how to decrease it. These are caused by the cPanel update script. There was a cron set for everyday at 2:00 and once I moved the time of the cron, the time the errors occurred moved to that time as well. My main problem was that I also backed up my server at 2:00 and I guess it was just too much for the server to handle and it would crash. Once I started to move some things around, everything started to work fine.