same here...... been happening for a few weeks in Michigan (detroit area and northern Mich)...... there's been a few threads in the last couple of weeks about this happening all over the country.....
i've tried everything short of a complete restore..... it's gotta be on AT&Ts side... .... luckily I don't MMS a lot, but the few times a week I do I expect it to go thru and 1 out of 20 times maybe..... (we pay all this money for this phone and ATT has nothing to say about something as basic as MMS)...