Network Time Out

I’m having a problem with a couple win95 pc’s timing out on an NT based LAN. When I reboot the machine and attempt to log in for the first time it takes a much longer than on other machines and doesn’t map all of the network drives. After that initial login procedure, when I log off, and then back on again I log in fast with everything mapped just fine. The NIC’s are running at 100mbs so they should be logging in lightning fast every time.