Xperia U: Network state is shown as UNKNOWN, data connection not working

I'm using stock Sony Xperia U. Data connection was working well until yesterday. All of a sudden I can't access 2G/3G data, it shows network state "UNKNOWN" when checked with the code *#*#4636#*#*. I've tried flashing custom firmware, stock etc, but in all it shows network state "UNKNOWN"