The regulator voltage of 3.0V is too low. The minimum for the ENC28J60 is 3.1V according to the datasheet, and I've noticed erratic behavior in the 2.9V - 3.0V range which is around the level of the low battery indicator. For example, at 2.95V my ENC28J60 won't startup 50% of the time.
I suggest 3.3V for the regulator if using ethernet.
The regulator voltage of 3.0V is too low. The minimum for the ENC28J60 is 3.1V according to the datasheet, and I've noticed erratic behavior in the 2.9V - 3.0V range which is around the level of the low battery indicator. For example, at 2.95V my ENC28J60 won't startup 50% of the time.
I suggest 3.3V for the regulator if using ethernet.