DI-524 One wireless connection makes others not ok

This is unusual, as it seems the router is allocating two pc's the same IP address.

Go into your routers settings (internet browser and type the router address, eg 192.168.1.1)' and look at Client DHCP list and look at the IP addresses that each pc has been given and see if two are the same, they should be one digit difference, that being the last.

Also go into the properties of both your pc's wireless cards and ensure that they are set to obtain an ip address automatically.