My question is essentially the same as that discussed here, but I have tried everything mentioned in the discussion there and none of it has solved my problem.
To briefly summarize the problem, every time I open a thread to send a text (SMS) message to my wife, the same fragment from a previous draft text I once prepared but did not at the time send re-appears in the text entry box as the beginning of my next reply. I have repeatedly deleted all drafts appearing under Menu/Draft (floppy icon). I have deleted the entire thread of prior texts with my wife and started a new thread, hoping to break the connection, only to have her send the first reply in the new thread, and find the fragment there again when I began to reply to her. I have tried just sending the fragment to my wife to "clear the pipes" (warning her that it wouldn't make sense but I was doing it to solve this problem). I have edited the fragment and kept one word of it mixed into an otherwise new message, hoping it would consider this draft to be completed and sent once and for all. You name it, I have tried it.
My phone is a stock HTC Thunderbolt on Verizon. I previously had the Handcent SMS app installed but deleted it, and the problem is still occurring in the regular Android (or Sense, I am not sure which) messaging app.