Based upon your description, it's kind of hard to tell what the problem is. But here are some things to try.
on each machine, do a start->run->"winipcfg /all". in the middle is a drop down box. Select your NIC. Then look for IP address and Gateway and DNS settings. Make sure you don't have any duplicates.
On each box, ping 127.0.0.1 This will test your TCP/IP stack
ping the IP address in winipcfg. This will test binding to NIC
ping another IP address on your local lan. test the wiring
Ping your wingate box
If all the above work, then make sure that all your machines have the wingate server set as their gateway. try pinging some site out on the Net.
Are you using wingate in proxy mode, or NAT mode?? If you are in NAT mode, then everything should be good to go.
If you are in proxy mode, then you need set your browsers to use an HTTP proxy. If you are running in proxy mode, I would try to switch to NAT mode, or you might check out Sygate 4.0. I think it's functionallity is a bit better, and it was pretty easy to install, and configure all around. YMMV.