I have wireless setup with laptop and tower, it took bit a time. Is the wireless hardware and software installed? Is the wireless properties set? I used ad-hoc. Is your firewall allowing your laptops IP address?
I had something similar with a guy who visits site occasionally. He never lost access but the message always came up about 30 secs after initial connection to the router. Tracked it down to a utility (DELL I think) that was competing with XP settings. The only way round it was to disable the wireless device through XP then use the utility to re-enable it and then always access the settings through the utility. I can't remember the details more clearly than that, sorry.
This thread is now locked and can not be replied to.