I'm using Cepstral David and Callie (version 5.1) with a windows sapi5 application and seeing a very long delay / hang when trying to stop speaking.
The problem can be duplicated using the Microsoft Sapi5 SDK demo application (Sapi5 TTSAPP). Load around 1000 words into the text entry box, press the speak button, wait a second or two, then press the Stop button. On my system, the app hangs for around 15 seconds before the Stop seems to complete.
Is this a known problem or possibly a problem with my install?