Balix,
From what you describe, my instinct is that it is either a TCP/IP issue or a login issue.
I suggest the following:
1. From the router's menus check that the wireless machine is listed under attached devices.
2. If the router is set up to be a DHCP server check that the laptop is also set up to use DHCP. If the router is using static addresses (Unlikely unless YOU have set this up) make sure that the net masks match.
IF the TCP/IP set up is OK then it is likely to be a login issue and that depends on what you re trying to do.
HTH
EG