For her iPad issue, he probably changed the wireless security type between WEP/WPA/WPA2, and the key type AES/PSK-TKIP and maybe the password; check to see that her settings for those match the router settings.
To clear up the issues on the Linksys, I would hard reset it with the reset button on the back and then manually set it up again correctly; and delete any networks on your computers that are no longer valid.
You might also check to see if there is an updated firmware for either router.