Okay this brings it to about 10 people and seven threads I've found on this subject alone, and so far, other than "Download Handcent" or "factory reset" I've seen no fix, and nothing from the Forum moderators.
Anyone else have any luck?
Received an MMS message with a photo, after it downloaded and I clicked the message a pop-up came up "A read receipt will be sent, Yes/No" I clicked Yes thinking I had to in order to view the message. Suddenly now that "text message not sent" notification keeps popping up.
I've deleted the original message/photo, rebooted the phone (soft reboot, on and off) twice, even cleared the messaging and text messaging caches in the Applications settings, no luck.
Got a non-rooted D2G with stock app.