1. Open Help menu | About | click "Application Data Directory" link | and the folder should open.
2. Close the About window and then fully exit Toad.
3. Go one level up and rename the "Toad for SQL Server x.x" folder (add OLD in the end of the name).
4. Restart Toad, and do NOT migrate settings if you are asked to.
5. All the predefined connections should be gone.
6. Connect to database without checking Auto Connect checkbox.
If you would like to transfer over your Saved Connections History file, go back to the OLD folder you renamed earlier | copy the "Connections.xml" file (make a Back-Up of this file as well in case of problems) | paste this file in the newly generated "Toad for SQL Server x.x" folder.
Re-test the issue first before transferring over your Saved Connections History.