Great question stuwing. What error message are you receiving is a great way to start because it could tell us what is occurring and give us an idea of where to start. Also, have you tried power cycling your phone, and it only to/from a certain person or anybody? You could also have picture messaging blocked on your account which could allow for calls and text but prevent pictures.
You can check your blocks online via my Verizon or with customer service by calling 1-800-922-0204 or *611 from your mobile phone.