I have a macbook and macbook pro, both 2007 running 10.5
Macbook connects faultlessly to my wireless router, macbook pro recognizes the network but cannot connect to it. Macbook pro works when cabled directly to the router. Have entered the WEP address correctly, etc but it will not connect.

Any ideas?

1. Make sure the network is setup with WPA2

2. Set up the locations you will be using the most. Use Automatic for everything else

3. Manually enter the DNS information for your ISP

Reference:
[1 (http://www.mac-forums.com/forums/schwebs-lounge/185652-macbook-pro-wont-connect-network-help.html)] Basic wireless settings for Mac
[2 (http://www.mac-forums.com/forums/internet-networking-wireless/150044-d-link-628-macbook-wireless-issues.html)] Enter ISP DNS

Check you keychain for any saved passwords for the network you are trying to if you find one delete it. Then open System preferences and check the time, and clear any saved wireless network that you so not regularly use, restart the computer and try again.

Might want to check configuration. Some mac's look for PPOE handshake which most routers don't support from ISP.