can anyone help with new modem/router query - linksys N wireless

just upgraded to a linksys wireless modem/router;
setup and internet work fine on wired desktop;
problem - toshiba laptop will connect wirelessly but not have access to internet.
other laptop will connect to my new modem/router and get internet access via wireless; and my laptop will connect to a mate's wireless network and access internet.

so problem seems to lie specifically with my laptop's ability to connect to my new modem/router AND get internet - it will only get local access.

any suggestions? have tried getting updates for my built-in wireless with no effect. also tried different channels etc.

am out of ideas!!

should add: when i access mate's wireless and get internet access his wireless is G, not N; my laptop previously accessed my own network which was also G;
if i hardwire my laptop into the new modem/router it will have internet access too.