The wireless and wired clinets should have similar"network details" as they should be on the same network. So gateway, DNS and subnet mask same and a unique IP. How is DHCP managed? Does the WRT provide DHCP? What is an IP of a device that works? The IP of a device that does not?
What is the device that connects to the Intenet? DSL modem? Cable Modem?
The devices on wirelsss need to ahve the correct IP, Subnet Mask, Gateway and DNS server(s). As the wired clients work, they must have the needed confguration. The wireless will need the same except for the actual IP. The router will "sort" things if properly configured but that does not seem to be the case. It may be taht the DNS is not correct on wirelss clients. Can you PING a web site by IP froma wirelss clinet? From a working system PING say Google.com and note the IP that replies. Go to a non working system and ping the IP. If it replies, the issue is likley DNS.
Can you provide an example of the IP of a working client and a non-working client? That could help. Simply something like 192.168.1.X or whatever with teh X replacing the last octet