The reason I have heard is because the motorola i1 only ultilizes MMS and since its iDEN it can only handle one type of data coming in or going out at a time.
so if your making a call, text will not come in until you hang up. Same if you are sending them while talking on phone they will not send until you hang up.
works the same way if you using the PTT feature.
I also hear if you have your gmail or POP3 mail server checking for new mail ever minute or two(this can be changed in actual mail setting when you go into mail app)
it messes with the messaging system. hopefully it will be solved with the supposed enabling of true SMS in October or when they do the bug fix update in November. (Even then phones that are being used wont have true SMS automatically)
So yeah its basically the network not the phone I personally blame sprint not allowing iDEN phones to have SMS already. Seeing that these phones have always had the capability to use to different types of messaging systems.
Question concerning the pics sounds weird.
I would have them just try sending the pic with no text and see if that works.