[Problem]
You are using ircgraph to log several things on your irc network and make graphical output in html format with it. But, for some weird reason, after a few hours or days, it appears to stop logging, even tho the pidfile is still there and a ps auxn shows, that ircgraph is still running.
[Solution]
Connect to your IRC Server per IP rather than per Domain Name. If, for some weird reason, ircgraph gets disconnected and has trouble resolving the Domain Name, it will hang out on the network without doing anything. This problem is rather simply solved by connecting per IP and using the packages own little helper, a little script that checks for a pidfile and ircgraph running, and restarts it if needed. You should run this with cron - hourly will do for most people. Some might want to check every minute, but the script doesn't really need much CPU time or anything, so that's not a problem.