I see. Well, to be honest I'm out of ideas then. The buttons you mentioned are sort of "reserved" (see Arduino expansion board user guide,section 9.1), I don't really know if and how you could use those for restoring the firmware.
However it does look to me more like a hardware problem, I can;t believe the firmware got that deeply corrupted so that it displays nothing on the serial port. I'd rather suspect a port failure or something. Maybe it's a good moment to try returning it where you've bought it, claiming HW failure?
As a sort of a last resort, you could try forcibly reflashing it, using the same flashall approach, but adding a "--recovery" switch. For that you'd either need to have an xFSTK utility built or slightly modify the flashall script, the modification is described in the ubilinux thread (you need to add the -R switch and a dfu-wait, AFAIR). Then you'd just start the script, power on the board and see if script recognizes it. If it doesn't - try restarting the script and pressing Reset (SW1UI5) button without powering off the board. This technique usually worked for me when script didn't want to see the board using the canonical start script-power on the board approach.
CMata_Intel, DiegoV_Intel, JPMontero_Intel - if you guys have any other ideas, please chime in.