Firstly, your phone will have a warranty so can be repaired/replaced by Sony. In the first instance your mobile phone vendor should be able to offer assistance inregards to repairing it.
I would also suggest re-running the Update/Repair... I had it fail at the last stage on updating my son's phone yesterday and the second time it went through fine. It may be worth trying it through both the Sony Ericsson Update Service and if that doesn't work try the PC companion programme. It has become apparent with the whole firmware update thing that the SEUS and the PC companion do things in a slightly different way so worth a go at both.
