Slow ethernet network with emacs

[bazwel1962]

Our small school is running 10 of the latest iMacs OS10.5.7 and about 25 eMacs running 10.4.11 all connected to an Xserve running OS 10.4.11 server through an ethernet network through 3com 10/100/1000 switches. The iMacs connect fine to the network, logging on to them takes place quickly and all applications respond promptly. The eMacs however are very slow - it can take up to 25 minutes for a single computer to log in. Even once they are logged in the applications are responding very slowly, a simply typing can result in severe lag. I feel that I'm missing something fairly obvious here, but for the life of me.... Anyway, any suggestions about areas that I should be looking at would be great. I am not, however, a tech - just the guy at the school who knows that little bit more about it than any of the other staff. The eMacs have been recently reimaged and a few have been wiped and reinstalled from scratch and it made no difference to the problem. Any help, advice, suggestions would be truly appreciated.
Thanks and Cheers

[ElDiabloConCaca]

Can you provide a diagram of the network setup? Perhaps the eMacs are running through more than one router, or there's some DNS funniness going on...