Did you change anything before this happened? Especially uninstall or disable any apps?
It's almost certainly a "your phone" issue rather than a Google one or a HTC one, but just knowing that something doesn't work is rarely enough to diagnose the cause of it. What app is providing the voice input? What happens if you manually change your default keyboard app? What happens if you clear the cache of your keyboard app, or clear its data? If you uninstall all updates to the built-in keyboard? Are you having any other problems (e.g. failing to recognise touches in some places)?
I suspect that a factory reset will fix this, but it would be better if we could figure out a less radical solution.