XV
I recently had a somewhat similar situation - machine just booted to a blank screen with a flashing cursor. Cutting out a long and tedious story - I had at sometime in the past changed the Boot Sequence to boot from a USB device, and then from the HD. This went undetected for some time as I (nearly) always remove USB devices after shutting down the system. But on this particular occasion I had left a USB memory stick plugged in - and it took me quite a while to realise what was happening. So - have you changed the boot sequence at some stage and not changed it back? Just a thought - it might simply be that and not the Android?