Flashing a new Debian image to the Beaglebone Black, it crashed due to a power outage.
After the incident, the Beaglebone does not boot (at boot time, the four LEDs stay lit), nor can be flashed.
Connecting to serial port, I can watch the boot logs and enter to U-Boot terminal.
U-Boot 2014.04-00014-g47880f5 (Apr 22 2014 - 13:23:54)
MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
*** Warning - readenv() failed, using default environment
Net: <ethaddr> not set. Validating first E-fuse MAC
Hit any key to stop autoboot: 0
gpio: pin 53 (gpio 53) value is 1
Card did not respond to voltage select!
mmc0(part 0) is current device
Card did not respond to voltage select!
gpio: pin 56 (gpio 56) value is 0
gpio: pin 55 (gpio 55) value is 0
gpio: pin 54 (gpio 54) value is 0
mmc1(part 0) is current device
gpio: pin 54 (gpio 54) value is 1
1590 bytes read in 6 ms (258.8 KiB/s)
gpio: pin 55 (gpio 55) value is 1
Loaded environment from uEnv.txt
Importing environment from mmc ...
Checking if uenvcmd is set ...
gpio: pin 56 (gpio 56) value is 1
7307264 bytes read in 453 ms (15.4 MiB/s)
** Unable to read file initrd.img **
reading /dtbs/am335x-boneblack.dtb
62752 bytes read in 15 ms (4 MiB/s)
Kernel image @ 0x82000000 [ 0x000000 - 0x758d58 ]
## Flattened Device Tree blob at 88000000
Booting using the fdt blob at 0x88000000
Using Device Tree in place at 88000000, end 8801251f
And here we have the four user LEDs lit.
Avoiding the option of having a hardware issue, I need to restore the kernel or a whole Linux image.