Internet of PC hardwired to router not workng

Hello,
i dont know what happened to my router. it has been working well but just this morning, my laptop's internet connection was lost when my sister turned on the computer harwired to the router and used its internet. i just clicked on some stuffs in the computer hardwired to the laptop, and suddenly its internet connection stopped working. it has windows vista by the way. everytime i click the "connect to a network", it asks me for a username and password. i typed the username and password i assigned the first time i installed the linksys router but it says, "failed to connect to broadband connection". weird thing is, now it's the internet connection of the laptop that uses wireless connection that's already working. help?