red light flashing!!!..well this only happens on my K750i when the battary is completely drained, but in your case, you said that you tried to charge it and it didn't work, so I think it is something with the battary connections!!!maybe...
best solution since you still in warrenty is the SE service center, you pay for the service when you bought the phone, so, it is time to get a use of what you paid for...