Hi
I have noticed the same issue with Blue and Me with my HTX 8X. The only workaround I have found is to hit the send button on the phone.
I just wonder is it a button on the steering that requires pushing to send the text message reply instead of saying "SEND".
When I have some time to spare I am going to have a look and see if this is case until Blue and Me or phone receives an update resolves the issue.