But you didn't share much detail.
Many don't check if MAC filters are turned on. Either add this new device or disable that in the router.
Many use WEP and there are issues there. Set the router to WPA/WPA2 and try again.
And your post has an ODD statement in it that makes me think these routers are not under your control. For a test, go to a location with free wifi before you start making changes and make this worse.
My girlfriend has just moved to China from London and can't seem to connect to the router in her flat. Details as follows:
Laptop: Samsung Q330 running Windows 7
Router make- tp-link tl=wr340g
She's gone through the usual "setup new wireless connection" scenario and although the laptop can see the various hotspots it won't connect to them (it shows "diagnose problems" and recommends the usual switch on/off routine- which she's done)
I wondered if it could be something to do with her IP address? She's checked the box on control panel which searches automatically for the IP address and on command prompt we've done ipconfig/release and renew. She gets an error message saying "no operation could be performed on LAN- disconnected media"
Prior to leaving she downloaded a VPN- I don't no if this makes a difference!
Any help would be much appreciated- we desperately want to SKYPE asap! Many thanks.