Several Macs losing network connection

[oocainoo]

We recently upgraded 20 Mac computers ranging from first generation G4s to dual 2.7GHz G5s (no Intel procs). Of these Macs, five constantly lose their network connection - no Internet, Intranet, network drives, printing, etc. This happens several times a day. Out of the five computers having this issue, three are G4 towers, one is a G4 cube and one is a G5. All the other Macs are fine after the upgrade. The 20 Macs are on two different subnets within the building and we have Macs on both subnets experiencing the problem. These machines run similar applications, were all upgraded in the same way around the same time, and are running 10.4.5. I am upgrading a couple of the machines to 10.4.6 to see if that helps, but I am not holding my breath. The computers a plugged into Ethernet drops. Four out of the five experiencing problems use DHCP and one has a static IP. I saw other people that were experiencing this issue on home and work machines, but no solutions. Please help. My users are getting tired of rebooting several times a day. THANK YOU!