My s3 has been crashing for days now.
In another obscure thread I found someone having problems similar, anyway they said the fix was as follows:
Settings > DEVELOPER Settings > Turn off Transition and Animation Scale.
I have now had a phone that has not crashed for about 6 hours. Which after the 4.1.2 upgrade hasnt happened for weeks.
Fingers crossed, I'll report back if it crashes again
Mr B
This solution quite worked for me too. my s3 did not freeze the whole day...