Zyxel P660HW - Wireless Router adsl modem set up...

Question

I have two computors connected to Zyxel P660HW - one wired connection and one wireless. Each connects to the internet successfully. However, when the wireless computor is connected to the internet the wired computor does not connect. Any thoughts how I can overcome this?I have tried connecting to each wired connection on the router but stiil the same the wirelss connection locks out the wired connection.