Can't really offer much help, but I looked into this a lot a couple of years ago when I had my OG Droid. At the time I used Handcent as well and loved it, but I started getting duplicate texts (all incoming, anywhere from 2-5 repeats). Didn't find a solution back then, and since upgrading to the Gnex, I experienced the issue again, with Handcent. Any incoming one word messages come in triplets. But that's it. If its two words or more, no repeats. I've uninstalled Handcent and used the stock and I had no issues after that. I like Handcent though, so..biting the bullet and dealing with it.

