Understand the concept of threaded SMS - problem is that the message thread doesn't show a new contact or start a new thread when a new SMS is received from someone new - all messages from all recipients appear under the same (first) contact/thread. This is also the only contact I can send an SMS to.
If I use the address book to start sending an SMS to a new contact, I can select the contact but when I press OK I get binned back into the same old message thread and the resulting text will only go to the same one recipient...