1. Using a free software update to your phone
With this tool, you don’t have to download manually FS, MAIN , and GDFS of your phone. There is a risk of step by step flashing and customizing. See my post how to update Sony Ericsson handset. (It’s very easy and safer!)
2. Hardware configuration
If the update above has successfully done, but the same problem occurs, it is no longer phone program damage. You may bring your handset to a mobile repair shop for checkup and they will do the right thing.