[toinejuan]

I know what you mean, I experienced this same issue also. I have found a solution albeit, it's not a simple one though. This is what you need to do, whenever you send a pic/video message, you will see the data bars, click continue and if they are no longer showing go to weather or even Sprint TV and hit update.
This will give the data connection the boost it needs to keep sending your pic/video. I have used the Diamond Tweaks program and that has helped tremendously, but this is the best method I have come across so far to keep the data flowing.