Connected but can't ping router or surf!

I have 2 XP computers and one laptop. Using an SMC Barricade wireless
router on ADSL. One PC connected to router by LAN cable, other PC
wireless, both connected and on the internet. The laptop connects fine
through LAN cable to router. WIrelessly I can connect to the router and
see shared files on both computers, but can't surf! Also, it times out
when I ping the router! I'm using DHCP. Have tried static IP and same
problem. Also uninstalled and reinstalled the wireless network card.
Any ideas?
Thanks.