Toad will hang after a second connection is attempted via the File - New Connection function when the Toad shortcut property is not set to run in compatibility mode for win 2000
Change the Toad Shortcut property compatibility mode to Win 2000:
1) Right Click on the Toad shortcut Icon on your Desktop.
2) Select Properties | Compatibility Tab .
3) Enable (check) the Run in compatibility mode option and select Win 2000 from the drop-down box.
4) Save the changes, then start Toad.