I had the same problem on my Moto Droid 1 with OS 2.2.1 and fixed it by doing the following:
- Open Google native Messenging app (the original Messenging App installed on the phone)
- Select Menu button
- Select Delete Threads
Problem solved!
P.S.
This deletes all of your old messenging threads, but nothing in this Post worked and I was ready to do a Factory Reset, so I can deal with it
