When i picked my Arc S up from charge yesterday it refused to start. Sony PCC didn't find it when connected to computer. After consulting this forum and trying different things i got it started by holding down the powerbutton while putting in the battery, the phone then works ok. PCC now find the phone and tells me it's updated. But if i turn the phone off i still can't start it whithout removing the battery. I tried to repair the software with PCC but when i turn off the phone and then connect the usbcable the computer just ask for QHSUB_DLOAD driver and PC companion don't start the repair. To get the phone started again i have to remove the battery. I have also tried SEUS with the same result. I haven't unlocked the bootloader or done anything else to the phone. It's months since i updated the OS.
everybody in this forum knows nothing. actually, my phone encounters the same problem as yours. mine is xperia play r800i. i cannot enter flashmode and fastboot mode using the physicals buttons. your phone's bootloader is dead. you need to flash another bootloader in order to make the casual flash mode and fastboot mode to be working back. sorry for my bad english. you can contact alejandrissimo at unlock-bootloader.com . i am sure he can fix your xperia too!
I was in the same situation .
I came out of the problem by pressing the Volume + , Volume - buttons, camera and power for 10 seconds .. the cel still vibrates off and turn on normal ... is not very good because I use my English translator ...
