clients accessing the internet

HI
im running Advanced server as a pdc with a modem on it to access the internet. i use sygate 3.1 as the dhcp and link to the modem , all my clients can see the network and all the accounts work ( 2X win 2000 pro, 1X win98se) ok my prob is that 1 client (my comp with win 2000) can access the internet but the other 2 cant even though all settings an pointings to the gateway are all the same , i should also point out that my comp is the omnly one with fixed IP address, the other 2 use dchp, anyideas? thanx