Network Accounts Unavailable

I have 35 macbooks that sometimes can and sometimes cannot connect to our network for login. We have the golden triangle running and if I login to a local account (admin) and establish the wireless connection then logout the Network Accounts become available. After that point it is a crap shoot on whether the macs hold on to the network after either going to sleep or restarting. Sometimes they will hold the connection and IP address sometimes not. Any thoughts??