Interesting happings on our CentOS machine
 

For two days our server has completely blocked out a few of our lasers. But today, just like yesterday the printers started working at around 4:00pm EST.

We could only ping the address of the non working printers once and get one reply and then just a hang. But at 4:00 everything started working. I immediately thought this would have to be something related to the Cron, but I haven't seen anything that looks like it could be doing it. I just wondered if anyone has ever done it. Just so I know what to continue to look for.

It's probably a network issue, could you ping the printers from different hosts? .. cron will often run the daily jobs at 4am not 4pm.

Thanks for your answers
 

Yes we were able to ping the printers in question from both the Windows network (interfaced with linux) and our other Server running Red Hat not CentOS. And I actually have a cron job that runs at 4AM for building a BI reporting system.

Is it running on Cups?

If yes. Is there only one instance of Cups or more?
I did have some time ago similar issue due to two cups servers running at the same time.

To Polinux
 

When you are asking are there two CUPS Servers, do you mean to CUP Servers running twice on one machine? or in your networked system as a whole entity.
We have both a CentOS and RedHat boxes running. each one has one instance of CUPS. The RedHat Box can print to all printers, even the ones that the CentOS can't reach. Also when attempting to ping the non-working printers we get one reply and a hang.

The other interesting situation on the CentOS machine is that we have two 1GB NICS at different addresses, all user used to attach via eth0 which is seemingly becoming very finicky. Many user have been switched to eth1. But for instance I am attached to 10 and don't have a problem.