Laptop and pc conflict when going online

I have just upgraded to a wirless router with BT broadband as my ISP. The pc is connected via ehternet cable and my laptop through wi-fi. Both can go online but not at same time. So if i am online with my PC and then go on with my laptop the PC drops out and the laptop works fine. If i restart pc it logs on to net then drops again as long as laptop is online. Confusing? I'm thinking it's an IP address problem.
Anyone have similar problems and solution?

By any chance is one of your computers using Vista? If so there might be a conflication of IP address problem. If you set static IP addresses on both machines this should sort your problem.

Chances are your probably right re. it being an ip addressing problem. Whats the make/model of the router?
In both pc and laptop, at the command prompt, type in ipconfig/all . This will show the ip address for each. If they both have the same ip, then theres a conflict either caused by having just one ip address in the routers ip address range (if dynamic setup) or just one ip address setup for both pc/laptop (if static setup).

Go to the router configuration settings (probably at http://192.168.1.1 ) and check whether set to dhcp or static.