Cannot see a wireless network on one laptop

I have set up a wireless network around a friend's but one of their laptops cannot see the router. The SSID isn't hidden and the laptop cannot see it even in the same room, whereas every other laptop and all of their smartphones are able to connect just fine.

The laptop is a 1 year-old dell, so I believe it has a relatively recent wifi card installed by intel. What is causing this problem? It can find neighbours networks fine, and supports b, g and n AFAIK with WPA/WPA2 which is what I set up the router as. Default channel is probably 11. Would changing this help?
It is running W7 also.

i would say the laptop isnt seeing the channel the AP is broadcasting on, drop the AP to 5/6 and see what happens. I had to do this recently with a 1 year old netgear WIFI PCI card

Cool thanks, I will update with results tomorrow when I fiddle with the settings.

Also check to see what is 'controlling' the WLAN card; the OS or a 3rd party piece of software? I've had issues with the 3rd party (intel, broadcom, etc) full software packages before. If possible, given the AP channel doesn't fix it, try uninstalling the WLAN package and re-install the baseline/WHQL driver only.

Somehow after rebooting it can find it... not sure what the problem was :S
It was controlled by the OS, same as all the other laptops in the house and now it works fine... thanks for the tips, might be useful in the future if I come across this problem again