> Any more thoughts?

Not many ;-).

You could try reinstalling SAPI5 - I couldn't find a runtime-only link, but
the entire SDK is here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=5e86ec97-40a7-453f-b0ee-6583171b4530&displaylang=en

Also, which voice are you using? Try different ones - MS Mary is about as
standard as you can get.
amiconn had a separate problem where he could get errors if he wasn't logged
on as an administrator; most voices worked fine, but L&H ones didn't.

-- 
pondlife