laptop cant find network

I have strange problem with my home network. (Asus WL-520GU with DD-WRT v24 on board). Today a friend came with his laptop (HP with LAN 2100 3B Mini PCi adapter), and then the problems started. It cant find any wireless network! I tried everything, from turning off security to upgrading friends network card drivers, but it didnt helped at all!
I've noticed, that when the laptop is rebooting, router 'see' it for about 10 seconds (used Wi-vizd 2.0 to check that) and thant it stops.

I have no idea what to do next, please help! I blame the wireless card, but friend says that it works fine at some hot-spots that he visits :O