help reqd. with WRT54G2 setup.

I recently setup a wireless network for an old friend of mine useing my own laptop (fujitsu siemens esprimo v5535) and his router(linksysWRT54G2). Everything went well,ie. router name,router password, ssid and login password.Seemed to be a sucsess(everyone who came into his cafe with a laptop,netbook or iphone got a user password and had full conectivity;local and internet).Everyone that is except me! I try to connect wirelessly and only get limited access(local), but if i connect to the router via an ethernet cable i get full access.What have I done?!!! Am I now the administrator for this network? Does my poor little V5535 "think" it's the host? If so,how can I remedy this?
I uninstalled the software that came with the router.I even removed it from my list of wireless networks,and tried to add it again.All to no avail!!
As any of you good people reading this can guess,I am not an I.T. tech.man, just a guy trying to help an old buddy!
Any help,tips or indeed solutions would be greatly appreciated.
Yours,
"in over my head!".