I have the same issue. I get the error "Unfortunately, Samsung keyboard has stopped" pretty much every day in the middle of texting, and I have to restart my phone by taking out the battery because the Samsung keyboard keeps trying to restart itself but it constantly fails and makes the phone unusable. The way it happens is the keyboard's response becomes supper slow (when I put my finger on a character, it types it 5 seconds later), and then the keyboard fails. Here is a screenshot of the error:
http://www.s3forums.com/forum/attac...ps-working-screenshot_2012-12-21-10-12-51.jpg
I contacted the Samsung support about this issue, and they told me to factory reset my phone. I reset my phone to factory defaults and only installed the essential apps, but I still have the problem. I loved the GS series up until now, but this issue is so annoying that it makes me want to go get another phone right now.
I have the AT&T version of Galaxy S3 btw.