Hi Litu. It's probably best if you do a phone reset by going into Menu, Settings, on General tab go to Master reset. At first I do do a reset settings and try it. This way, you shouldn't lose anything. If that fails try the Reset all. But this option will reset the phone to manufacturer settings. You can go to the sony ericson website and it will tell you how to backup your data.
Failing the above, the best thing to do is buy a USB connection cable (if you don't already have one!), connect it to your PC then go back to the sony ericson website and do a full software upgrade which is free of charge. Sony Ericson actually suggest you do this every 6 months.
Hope the above helps.
Nigel, January 2009
