limited or no connectivity message

I just got my Dell system and I tried to set it up with the wireless internet connection..

The computer is a 640m Notebook .

I already have another Dell notebook 6000 connected to the same wireless connection and it works just fine..

The new one It finds the wireless network but it shows an exclamation sign and when I try to see the available wireless networks it tells me that Windows cannot configure the wireless connection. It recomends to start WZC which overwrites the ethernet connection and then I have no internet.

Anybody can offer some advice ( I'm not very good at this wireless stuff ;)

The connection is an AT&T , DSL .

 

Thank you very much

Sandy