I have CM6 installed (though I've had this problem with what seems like every ROM or even just the plain Android update) on my Motorola Droid 1 (this is my 2nd Droid 1.... and still have problems)
I receive about 50% of my text messages on my phone multiple times. I used to just live with it, but it's starting to get annoying. I used to think that if I checked my phone the instant I got the message that's what caused it to "receive" it multiple times, but now overnight I'll get a message 3 or 4 times. In the past week it's starting to be large time gaps in-between now too. For example: I'll send a text, get a response from them at 12:30; I'll get that response 2 times... then at 12:36 I'll get the exact same response again 1 or two times.
Is this a ROM issue? Verizon issue? Android issue? Phone issue? It's so obnoxious... thank goodness I have unlimited texting or I'd be really ticked!