Airport issues - how do I change the channel?

My neighbour has just bought a wireless router, which keeps knocking the signal from my airport out, probably once every 5 minutes.
I was advised by a friend to change my channel which my wireless is on.

I did just this, the problem is, once changed the mac doesn't pick the connection up. Even if I try and add a new connection it cannot find it.

I have tried multiple channels, can anyone advise me how I can do this? I hoped it would be as simple as changing the channel and the mac picking it up.

Open Airport Utility, click on Manual Update, select the Wireless tab and change the channel. I've never had a problem with my mac picking up the change after that. Perhaps remove the connection on your mac and recreate it.

I opened airport utility before I changed the channel, just to get an idea of what I was doing. When I open airport utility I get the following error:

"Airport utility was unable to find any apple wireless devices. Please make sure the apple wireless device you want to set up is plugged in and in range of your computer, and click rescan to try again"

I have a signal, which is currently fluctuating from half way to full before going to zero after about a minute. If I scan for the device even when it is full, it cannot pick up the wireless device.

Anyone?