After thinking a bit, I remembered that when I was trying to correct other Internet connectivity issues that I had created an unnecessary broadband connection option in Vista. When I went to check my network connections, not only was this option still present, but it was listed as the default connection type. No wonder I was having such a problem.
After getting rid of this connection, the Connect Broadband Connection window stopped popping up. Here are the steps needed to take this action.
Step 1: Click on the Start button, open the Control Panel, and then select Network and Internet. (Click any image in this article for a larger view.)
Step 2: From the Network and Sharing Center category, select View network status and tasks.
Step 3: Pick Manage Network Connections from the Tasks list on the left-hand side of the Control Panel window.
Step 4: Look for a disconnected broadband connection. Right-click on it and select Delete if this connection was just created in error. If you sometimes use this connection and don’t want to delete it completely, you can just choose the Cancel as Default Connection option instead.