Network hiccup

I have taken over a small network of a NT server and 4 Win98 machines in our office. I have just installed Sybergen’s Sygate onto the Server for internet access for all Win98 machines. Each machine can see each other on the network and all can browse the internet, but we have lost the network connection with SQL server on our NT box and with our POS system. IS this a bug with SQL server? or does anybody have an idea for me to try?