Could you do a test ? When you're on that screen (mouse pointer on black screen) just flip your A600GS upside down or sideways for some seconds, does it the recover and get into the A600GS welcome screen ?
I had the same problem and some wire of the WiFi Antenna had gone loose and has shortened out the USB Ports (I guess) ... moving it while in that screen made it recover from that and it would load ...
