Are you using an alternate sms app?
It sounds like you might be.
If so, go into the settings in the stock messaging app:
Uncheck the box that says, "display message notifications in status bar".
Doing that should solve the duplicate message problem.
The path is:
app drawer>messaging>menu>settings>Notifications - UNCHECK THE BOX
As far as the mms not sending:
1. Make sure you have your new sms app (Hancent, Go, or whatever your using) set as the default messaging application, and make sure it is set to "Disable" all other messaging apps.
The path (depending on what app your using) should be:
app drawer>whatever new sms app you use>settings>application settings>Default Messaging Application>DISABLE
2. Make sure you have Data "Enabled" while trying to send a picture message.
MMS needs that setting to be on.
The path is:
menu>settings>wireless & networks>mobile networks>Data Enabled - MAKE SURE BOX IS CHECKED
3. Sometimes having the Wi-Fi on causes it to act up.
I still don't understand why. That part may just be a bug in the app.
To turn off Wi-Fi:
menu>settings>wireless & networks>Wi-Fi - UNCHECK THE BOX
**Data needs to be Enabled for MMS to work, no matter what app is being used**