Keyboard freezing when responding to text messages

2 nights ago i received a text and when i went to reply, it froze up my screen and would not allow me to input any info or exit that screen unless i reset the phone by removing the battery or holding the power off button for a LONG LONG time.When it finally resets it goes to a plain white screen and takes some minutes to show the main screen again.Does anyone have any ideas on how to fix this?