Macintosh computers cannot connect to router unless we re-start the modem and router

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http://serverfault.com – We have a small office network with DSL and a Netgear WNR-2000 wireless router acting as a DHCP server. There are nine devices connected to the router, wirelessly and wired. Whenever a Mac computer tries to connect, it's unsuccessful until we restart the router. Each of the possible devices that can connect to the network is listed in a table to assign certain IP addresses to certain MAC addresses. I am running WPA-PSK security. I can view the router status and see that the Mac's MAC address is visible to the router, but with a 169.* IP address, even though I'm assigning its MAC address to an (HowTos)