I have got on our network a virtual server (ESXI 4.1) running server 2003 with just our printers on it. It has been running like a charm up until last week. On Thursday, the head of ICT complained that his colour laser printer in his classroom was taking a ridiculous amount of time to print. Sure enough, a 5MB file was appearing in the queue, then spooling at around 100k/second meaning publisher files were taking minutes to print.
I sent the same documents to a mono printer in his room, and they printed out immediately. The resources on the server were not looking troubling, not getting over 10% in memory and CPU. No memory ballooning or VMK swap file usage. I have rebooted the VM, changed the drive the spooler is running on, as well as updating the drivers to the latest version of this particular printer, and also changing between the PCL6, Universal PCL5 and PS. The same printers located all around school, are experiencing similar delays, whereas before Thursday they were working just fine.
We had a problem on our network a number of months ago (network loop) which affected all of these same printers at the same time. The issue actually brought an error up on the printer itself and the printer had to be rebooted. This issue is not the same, but I just thought I would mention that these printers have had problems manifest just on their own model and no others on site.
Try a direct network print from a different machine, i.e. not through the server and see if that runs any quicker to rule out the server. Upgrade the firmware if avalible for the printers. Try isolating a printer and computer seporatly with static IPs and a crossover cable to isolate it from the network and try again.
If it is the network try using wireshark to look at the network traffic, you could also log on to the printers we interface if it has one and check its logs, CPU usage and possibly turn off pointless stuff like bonjur and IPX unless you have macs that you want to bypass things or a netware network from the cretatious that still needs support.
Yeah, firmware is running the latest version as a chap from OKI came out and flashed them all 2 weeks ago, and the website is reporting the same version. Tried a direct print, bypassing the print server and I get the same result. Wireshark isn't really coming up with anything conclusive but I am going to reboot the core switch at 3PM to see if there's some sort of faulty device causing an issue. All the pointless junk like Appletalk and IPX is disabled. Going to try a Xover cable in 10 minutes to see if I can rule that out.