Mobile data won't turn on till reboot I'm using a Samsung Vibrant (aka Samsung T959 Galaxy S) (Installed Jellybean). Sometimes when I keep mobile data off for a while, it doesn't turn on. I have to reboot it to make it work again.
It seems like a network problem and might not have anything to do with your phone. Try using data services by some other provider.

Also, try re-configuring the APN settings.