Not from what I've seen but if you just hold the backspace key ( * ) it'll erase the previous message and you can start fresh. Not much of a problem really.

I don't know if it matters if it's boost or not, but I figured the more information the better..

My problem, among many others.. Lol is when I recieve a text message, and I hit reply.. It leaves the previous message in there.. Is there any way i shut this feature off? It's driving me completely bonkers! :P