frequent client disconnects

I have a new g5 dual processor with 6 gb of memory at one of my schools. It is serving as the Active Directory Master. Clients are having no issues logging in, but are getting disconnected all day long. They get a message saying they have been disconnected. User homes are all on the server. Student homes and group shares are on an older g4 xserve. Server is running 10.3.9. I have another identical server at another school and have no problems with it. Network is 100 mg switched (cisco) with vlan trunking and spanning-tree portfast on all ports that have workstations on them. This just started around 3 weeks ago. I dont see anything in my server logs that says it disconnected a client. This problem is getting steadily worse. Any help would be great.