Have had this phone since launch and never had this problem before. I'm trying to connect it to my computer to transfer music onto the phone but the option on the phone to connect as 'USB Mass Storage' is not appearing - my computer is not recognising that any device has been connected either. There is nothing wrong with the USB cable as it is showing that it is charging when connected. I've gone into the storage settings and it is confirmed that it should connect as a 'Media Device (MTP)'.

Totally stumped. Any ideas?

Try another cable, just because its charging, doesnt mean its ok.