Connecting to linksys-g

My laptop was working just fine, connecting to internet via wireless linksys router, until this evening. I cannot log on to the internet. When I look at the WiFi Connection, it shows 2 networks linksys, with only 2 green bars and linksys-g with ALL green bars. I can connect to linksys, but very poor connection. When I connect to the linksys-g, I get a popup box saying no credentials are saved for this profile. Please enter the credentials below and it is asking for my User Name, Domain, and Password.

Should I use the same credentials as the linksys connection and where do I find them? If I should use different credentials, what should they be?

We just switched last week from Verizon DSL to cable DSL but it has been working fine until this evening.

Thanks!