I don't know specifically, but I had a similar issue after I tried a Siri-like app (I forget what the specific name of it was, but it was one that was still new and pretty much in a public beta). It appeared to force close every time I tried running it, but I also started getting a voice announcement of every text and I couldn't see where and how to turn it off.
After I uninstalled that app, however, my texts stopped announcing themselves by voice.
Is it possible you've got the same app installed and it's causing this?
|