Does it help if you go to Options -> Online, and disable "Toad Improvement Program"?
When that's enabled, Toad collects anonymous usage data (nothing specific about your schemas or data, just how you use Toad). But if there is a problem sending that data, it could cause a delay on closing.
If that's not it, you could take things a bit further by editing Toad.ini (do this while Toad is NOT running) and adding this under the [SETTINGS] section:
InternetAccess=0
Toad.ini is typically located at C:\Users\your_windows_user_name\AppData\Roaming\Quest Software\Toad for Oracle\14.0\User Files\Toad.ini
And if you want to take things another step further, you could also install the 14.1 beta. There have been numerous bug fixes since 14.0 in the beta (and not much in the way of new features).
You can get that here: Toad for Oracle 14.1 Beta
The nice thing about beta is if you find a bug, you can report it here. If we can reproduce it, we can get bug fixes to you quickly. New beta versions typically come out on Mondays.