Same here. I have an HTC Vivid, have had it for 2 years. I sometimes receive the same text a couple times, not a big deal, but since last night I've received the same text approx 50 times (no hyperbole). It was sent at 732 pm pdt, and it's always the same time stamp.
I then messaged that person on a messaging app and he said he had been sending me other texts that I do not receive, but my texts are going out.
I have rebooted, taken the battery out, taken the sim card out, deleted his contact information, deleted ALL of my texts (even saved ones), he rebooted (he's on an iPhone) - but I'm still receiving the same message a couple times an hour.
What else can I try? I depend on texting for the bulk of my communication so it's very hard to not have access to it.