Can't change my keyboard for messaging app... wtf?

[XxxXnoodleXxxX]

So I have a Samsung Galaxy S3. I've been using Smart Keyboard Pro for a week now. It was working fine. I restarted my phone and now it won't work. I went to the messaging app and it's the standard crappy Samsung keyboard. So I go to me input settings, and both the Samsung Keyboard and Smart Keyboard Pro are checkmarked, but the Samsung Keyboard is greyed out. I can't unselect it. I uninstalled SKP and reinstalled it, selected it as my input method, and all I've got is the stupid Samsung Keyboard.

What the actual hell? How can I fix this? It worked completely fine and now I'm locked out of it.

 

[B. Diddy]

In the Settings>Language & Input menu, is there a setting for Default Keyboard? Make sure that's set to Smart Keyboard Pro.