iPhone Won't Text Pictures

[MBP13]

Hi. I've had no problems with my iPhone for until about three weeks ago. For some reason, the iPhone won't send/text pictures to people, but I can get sent pictures from other people. I was able to send/text pictures, but now I can't. The iPhone will show that the pictures were sent, but they actually don't send.

What can be the problem?

 

[Kyotoma]

Make sure you have MMS enabled in Settings>Messages

 

[MBP13]

MMS Messaging is on. I've had this problem before and after updating to iOS 5.