MacBook Pro elbows out MacBook from Internet connection on AEB (802.11n)

Question

I have recently setup Airport Express Base Station (802.11n) to connect to Internet via PPPoE. I have the following:
a) MacBook Pro;
b) MacBook;
c) ITouch;
d) Wii
All four hook up to the AEB, and connect to the Intranet individually.
But the two laptops do not connect to the Internet simultaneously.
If the MacBook Pro is already connected, the MacBook does not. When I shutoff the WiFi on the MacBook Pro, I have to go through all the steps in the Airport Utility on the MacBook, to connect to the Internet. It works fine, as long as the WiFi on the MacBook Pro remains switched off. As soon as I connect MacBook Pro to the AE, the Internet on the MacBook drops out. The MacBook does however continues to show the name of my AE network (along with several others in the neighborhood) networks.
Internet Connection from ITouch and the Wii remains unaffected.
My intuitive analysis was that perhaps both laptops are using the same frequency or channel to connect to the AE. So I changed from "Automatic" to "1" on the MacBook Pro and "2" on the MacBook. It did not help despite more combination.
Any suggestion please.
regards ... Ajay

Answer 1

Ajay,
Welcome to the Apple Discussions!
Do me a favor, as so many others are experiencing this as well with multiple Macs on a network. I've suggested so many different things, but this one just came to mind while I read your post. Try this on all the Macs and let us know...
*Can’t Access Certain Web Sites / DNS Server Settings Issue*
I'm wondering if either or both Airport Utility & Network Prefs have proper DNS server settings. Try this
Launch Airport Utility.
Select TC on left.
Click "Manual Setup".
Select "Internet" from the toolbar above.
What's listed for "DNS Server(s):"?
Try putting in these servers from OpenDNS
208.67.222.222
208.67.220.220
Click "Update".
Your TC will restart with the new settings.
Next, launch System Prefs --> Network Prefs.
Select the service you usually connect with on the left (Airport or Ethernet).
Then click, "Advance..."
Click the "DNS" tab.
What's listed for "DNS Server(s):"?
Usually "10.0.1.1" will be listed first in gray. This refers back to the settings in the Airport Utility.
Nevertheless, it doesn't hurt to add the DNS servers noted above here as well.
Click "OK" then click "Apply".
Finally, reboot your Mac.
Now see if you have internet access all around.
Let us know if this resolves your issue.
Cheers!