I have got a BBB board with Angstrom Linux on it. Yesterday I have tried to update it to a new recommended Debian image.
After enabling flasher in mSD card I booted my BBB from it. On the beginning user LEDs were blinking in a wave pattern, one ofter another. After some 15 minutes all 4 LEDS started to blink simultaneously. On 60th minute the pattern was two short blinks, pause, repeat. Tired of waiting I powered it OFF. Now it refuses to boot from the on board image (probably got corrupted.). I get some stable cycle of LED flashes, and cannot connect to the BBB via SSH.
In this case power was provided by USB.
I tried to repeat flashing while powering BBB from a 5V PSU. The same result.