unable connect wirelessly from voyager2091C/ Imac

I have an Apple Imac computer with airprt installed. When I first joined Plusnet I set up the wireless connection on the Voyager2091router provided.It worked fine at first then for no apparent reason started dropping the connection. I also had to reboot the Router nearly every time i used the net. I decided to use the ethernet connection and it worked great. However as my wife wanted more space in the bedroom I had to shift the computer too far away from the telephone connection , so I need to connect wirelessly again.
I switched on airport in the computer ,disconnected the ethernet cable and used the systems preference assistance to set up the internet connection. The lightsturned green on airport but stayed red on internet, isp etc. The the Airport changed to sow "self -assigned ISP', this means it will not connect to the internet!
I have tried rebooting the router switching off and on "Airport" and the "Imac" all to no avail, each time I end up with the message "Airporthas self assigned ISP"
I have seen a post on the "Apple" forum with the same problem. None of the solutions there worked for me. Can anyone help a silly old man
Robbie

Don't own a mac but if all else fails you could try using a powerline adapter which would enable you to use any electric plug in the house to send the signal via the house wiring. You need the two plugs and an ethenet cables. one ethernet cable plugs into your lap top / computer and the other cable into the modem with the plugs in between . Good for computers and games consoles.

My modem /router is upstairs with my computer but and I have Playstation3 downstairs and use this to connect to the modem / outside world. You tend to get faster speeds than wireless.

I use a Netgear HDXB101 ..you wont get 200mbps but you do get fast enough speeds ..faster than wireless anyway.

Edited by deleted (Fri 21-Nov-08 21:19:10)

Change the wireless channel.