I may have found some information on my problem with the duplicate text messages being sent. The problem lies in the threaded application. If the app gets completely closed without receiving confirmation from the receiving party then it thinks that it never went through so the next time you open it or it opens itself to receive a text it will resend the last message. Then if you quickly read it and close it again it goes through the same problem again.
I found that people in the treo forums were having the same issues. Since I was using pointui and for some odd reason it closes every app when your done I kept having this problem occur. I changed some settings today so if I turn out to be wrong I'll let everyone know.