knowltona:
Hello and welcome to the forums.
My first suggestion would be to ask him to power cycle his wireless router (remove the power for a minute or two and then plug it back in) see if he is able to successfully connect then.
Something (I don't know what) may have corrupted his previous profile for his connection at home.
In which case he should open the network and sharing center and from the left column select "Manage wireless networks", from there he can select the problem wireless profile and right click and choose properties and exam the security settings and passphrase, etc., and edit them if he thinks the are wrong, or better yet, just select it, click the remove button and then add a new one with the proper information.
Failing all of the above he might want to arm himself with his router documentation, reset it to factory defaults by using the recessed reset button on the back and see if he can connect then. If so he can go back in and reconfigure his wireless security as this action will most likely reset the router to "Open" (no wireless security).
Keep us posted and thanks for joining our community.
Regards
Randy