Sony Ericsson :: W395 - Playing Music Suddenly Screen Frozen With Multicolored Dots

I was playing music through the Walkman player, when the audio suddenly cut off and a very loud buzzing/crackling replaced the music. The screen had frozen, and the buttons had no response. The screen then exploded in a rainbow of multicolored dots, like that on a TV with no signal, before turning black. Now I cannot turn the phone on. I have tried taking the battery out and replacing it, and charging it, and holding the power button for ages. I have also connected it to the computer via the USB cable, but there is no response on the computer or phone.