Can’t surf on wireless network

I set up a wireless network with two Win98 machines. Linksys router. One computer hard wired. Other computer wireless(linksys card). Both working sharing a cable modem. Added third computer. Linksys card configuration says connection is good but I can’t surf. Can’t ping other two machines or router gateway address. Can’t be pinged. Rounded up usual suspects, but now going around in circles. Help. Please.

Mark