Welcome to Android Central! Are you talking about only the homescreen, or in all other apps as well? Does it persist after a reboot? How about after wiping the cache partition? http://support.t-mobile.com/docs/DOC-5744
You can check if the orientation sensors are working correctly with an app like CPU-Z.
If you rooted and deleted Samsung Hub you will need to upload a file to fix. I am not yet able to upload a link to the information, but perhaps someone else can if that's your issue...