My Wife is having the same issue on her Bold, and Mine works fine, 4 days dealing with AT&T comparing plans and still not fixed. It's ticking me off since she MMS me back and forth alot you know when her and I are out of town ect.
AT&T is ticking us off... No one knows what the issue is, from media net being added then removed then added again , to sending us to blackberry support then back to ATT. it's a joke.
Ill let you know if we ever fix it, keep us in the loop as well.