Aw man that sucks. And I've tried everything through AT&T they know what we are up to and if it involves anything to do with the iPhone and mms they just say they can't help (and we all know they can).That doesn't work for me either.
All you can do is try resets, toggling airplane mode, and make sure your apn, user, and password are correct. Oh and sometimes resetting network settings can help. I tried all these multiple times, so maybe that's why I can send them at all, oh and I left out that I can still get them. But earlier I got a few of those viewmymessage sms's so I'm thinking the combination of things I did messed something up in a good way.