Lan/Wan

Hi, thanks for reading.
I recently set up a wireless network for 2 computers ( after a lot of hassle ) with an SMC barricade. The guest computer is connected and works fine. The host computer, however has a bit of a glitch. The connection to the internet works well over a LAN, sometimes for hours, but every now and again a WAN connection pops up and takes over. I wouldn't mind, but it's connection is sporadic. It will transfer well for a few seconds, then cut off for a few seconds. I can 'disconnect' it, and all will be ok til it next decides to 'play' . This makes it very frustrating for webcams, downloads, etc. I cannot delete the WAN, and there are no 'settings' to play with. I am semi-literate with computers and any help would be much appreciated. Please ask for more info if needed, but include instructions as to how to get it !. Thanks.