I was flashing Debian latest update into the BeagleBone Black. I wrote the image to sd card and into the board and plugged in power while boot button pressing down. The four LEDs lit up correctly. After some blinking the power led and USR02 is lit up. Even after one and half hours nothing happens. Is it flashing or has anything went wrong.
It sounds like your power supply is not beefy enough.
With a Category-10 (fast) micro-SD card, the unit should flash the eMMC, or read the eMMC image in about 9 minutes.
A slower uSD card might take a little longer. I can not imagine either the read or write process taking nore than 20 minutes.