Visiting Computers Can No Longer Connect

Hello,
I have a Linksys wireless router and I have no trouble connecting to the internet with my desktop computer or my laptop from anywhere in my house. I have relatives visiting that were using their laptops for the first 3 days but can no longer access the internet. I can see that they are connected to the network and signal is good but still no internet.
When they trouble shoot their laptops, they are given a firewall message, but I have turned the firewalls completely off all machines and still no luck.
Can someone help?