Studio XPS 435, Windows Vista - Internet Explorer Cannot Connect Message

Last month I was all of a sudden getting the following message from Internet Explorer - Internet Explorer Cannot Connect to the webpage.  This affected my wireless router connection as well as my phone service which goes through my cable modem as well.  After several, several calls to my cable company, internet provider and dell - the only solution they could offer me was to backup my hardrive and reinstall Windows Vista.  I did this and am slowly reinstalling everything, however now that it is a month later, I am still getting the error message.

Can anyone help me with this ? We did everything from test my modem, reset IE7, clear history, set IE to automatically get an IP address and test my connection.  It seems to be working ok for now, slow but ok.  So I decided to reconnect my phone and wireless router. When I do so, I lose internet connection again and I'm not sure why.

I'd appreciate any help at all. This is driving me nuts. Thanks !