i have a blackberry curve from tmobile and i had the same problem.here are 2 things i tried doing. instead of going to the actual picture and hitting send thru mms i would go to the message section of the phone and choose compose mms. that seemed to work. but before that i had the same problem and what the tmobile people told me was that it was because i didnt have a blackberry plan on my phone which i thought was weird. i got the plan for 20 bucks and the problem stopped. hope this helps