im using an ethernet shield ENC28J60 and i can't use the sample codes in the Ethernet library files and all the codes available in the net if it is using an include file Ethernet.h ..i manage to download a library named ethershield and it works! does this means im off with Ethernet.h and stock forever with the ethershield.h codes only??? =( =( =(
The Arduino ethernet library is based on the w5100, not the ENC28J60. So you must use the library for that IC. 
Take a look at this post -> Arduino Forum