Network home logins slow and hanging

We are having a difficult time with our lab and laptop cart machines hanging during the login to network accounts. When we reboot the machines, it will usually be ok. When more students are logging on concurrently, it has a higher failure rate. The clients are 10.4.7, the home directory server is a 10.4.7 and the OpenDirectory server is 10.4.7. I'm having very little success tracing the source of the problem. I'm not sure if it's network related, OD related, AFP related, user home directory or client related. I've attempted removing the directory services preference files, reboot, rebind...this doesn't improve anything. I've tried simply resetting passwords along with recreating home directories. Anyone have some troubleshooting directions that I can follow?