If you are making changes to the Speech engine, then this will cuase the problem.
I discovered that early on. When I was first experimenting with Hal, I wanted to use a speech rocognition engine that supported dictionary editing. I also needed a Voice that I could go into and train words individually (because no matter how many times you run the Training Wizard, it will not learn the proper pronounciation of a "not so ordinary" name). I changed the voices around alot and anytime changes were made to the SAPI settings, the speech would be gone.
Getting the speach back is as simple as exiting Hal and starting it up again. This will re-initialize the SAPI settings that were changed.
I would suggest that you find the voice that you like, make the SAPI changes, restart Hal and you shouldn't have this problem again.
Just remember, if you make changes to the speech configurations, you may need to re-initialize Hal.
-=Rick=-
