Wireless connection issues with Macbook Pro?

I have three computers in total. Two PCs and one Mac (macbook pro new one) Before I had my Macbook pro I never had any connection problems with either of my desktop that is connected through ethernet and my girls PC wirelessly. The modem/router is a new Gateway Router/Modem.

The modem has five lights:
-Power

-Ethernet
-Wireless

-DSL
-Internet

Randomly the two last light start flicker green or red. That makes me lose my connection on my macbook pro and my girl rarely loses at the same time I do. After a few seconds the light are solid green and Im good to go. I have already had a technician over and we checked it out and it always seem to have with my macbook pro only. ATT has already changed my router/modem. I dont know if i made some mistakes when I set it up.

* on a side note
I have had ATT service for almost three years and never had any issues. This issues started when I got my first macbook pro in June 09, so I thought it was the macbook pro so I went to apple and they replaced it, and with the new one the same thing happened. Also in the time I was waiting for my macbook pro replacement I used my PC and didnt have any issues with the connection.