Excellent wireless signal but no internet connection and Error 797

I have read all the forums and have found no help with my problem.

My Inspiron 6000 laptop is receiving an excellent wireless signal which never drops off but it will not connect to the internet. For some reason it is trying to dial to my modem - which is not connected hence why I get the Error 797 message.

I have connected to the internet in the past wirelessly with no problem but I noticed a while back that my laptop would not connect to my Universities wireless signal despite it working for over a year with no problem. I am now finding that I cannot access the internet (or log into MSN) despite having an Excellent connection.

Any help would be greatly appreciated as I am ripping my hair out here.