It is a manufacturing fault with xperia phones. (they will not agree)
I have had 2 xperia U phone break after 3 months and was refused a warrantee fix.
It is the tiny center part of the charging socket, it broke off on both phones within a week of each other.
After many calls I got nowhere with Virgin as Sony will not accept it is a fault and will not let Virgin fix or replace.
I have never seen this fault on any other phone, ever.
You can get replacement bits on ebay for a few quid, so it must be common.
http://www.ebay.co.uk/sch/i.html?_od...+port&_sacat=0