Everything is good now. No "Unfortunately setting has stopped" messages.
This is what I did:
- Unrooted via SuperSU
- Reflashed Stock ROM via Odin (ROM downloaded from SamMobile)
- Booted into Recovery Mode and did wipe cache and wipe data/factory reset
- Reinstalled all apps via AppBrain
- Spent 2 days reconfiguring my apps.
I didn't do any restores with Titanium Backup. That may have been the cause of the original problem.
Thanks everybody for your help