Sony Ericsson :: Vivaz / Phone Battery Died

I am not sure if others have a similar problem.but here it goes.so I got my Vivaz Pro in Hong Kong around July and I brought it back to Toronto, Canada.The phone is nice all along. However, in September (2 months after I bought the phone), the battery is starting to warn out for some reason.I have charged it for the whole night and it only charges for half the amount.Sometimes, is not even charge for the 10%.So I have thought is the battery's problem and got another back up battery.But nothing have changed, the phone is still not charging the battery.I read somewhere that this problem is because there is some error in the phone's motherboard itself, not a battery problem.Can anyone verify the above information?What should I do now since I am in Canada and Vivaz Pro is actually not out in Canada?My phone is still under a 1-year warranty, but I am not too sure if this goes international (like I can still send it to Sony Ericsson Canada for repair?).Someone please help me!