MacBook kicks Powerbook off wi-fi network

Hi,

This is a repeatable and very frustrating scenario.

1. Powerbook (last revision) is connected to wireless network provided by a D-Link DI-524 wireless router.
2. MacBook connects to network (from anywhere in the house).
3. Powerbook loses signal to network and if it detects the network, returns the "Unable to connect to ... Try Again/Cancel" message.

modem settings:
full-bridge mode
router settings:
wpa-psk encryption
uses g-only
computers:
ip addresses are different

Any thoughts on why this might be occuring?

Cheers!