Enc28j60 Power issues
I can't find a datasheet on that dev kit, but I think I know what the problem is.

If you go to the datasheet of the IC and look at Figure 2-4, it shows that you will need a level shifter to bring the 3.3V output of the SO pin up to 5V so that the microcontroller can read it.  This is true of the /INT and /WOL pins as well.

If you're lucky, then your specific microcontroller can also be run at 3.3V.  Check your datasheet.  If so, then just power it from your 3.3V rail, and there shouldn't be any problems.

If not, then there are a lot of options out there to perform the level shift.  If you need help with this, please post another question :)

Good luck!