Why does one of my laptops connect wireles to my newly bought modem but the other only connects for like 5min?

my tobisha laptop connects fine to the internet on my modem but my other laptop doesnt when i try to connect it does for like 5 min. once when i tried to diagnose the problem and it says "if you have access to this firewall then configure the firewall to allow connections through TCP port 80. if you dont have access contact your network administrator or internet servers provider." what should i do? btw its a private network and the firewall is off on both laptops.