OK if you have got the PC Companion connect the phone up and go to the software update. It will tell you that you are up to date but if you are having problems then use the repair button which should be on screen.
If this doesn't work download Sony Ericsson Update Service and follow the onscreen instructions, from memory select your phone and then it tells you to connect the usb to the PC and then whilst holding the back button insert the usb connector into the phone. It should then read the phone and tell you that you can release the back button. You should then be able to select repair from there... but it is a step by step so pretty easy to follow.
