Are you sure your board layout is the reason that it failed? Board layout can be critical, but more than once I've been pulling my hair out trying to get something working only to realize I've set one or more of the fusebits wrong in the AVR or plugged something in backwards. Depending on what it's doing, you may be able to tweak things a bit to get a less than perfect PCB layout working. A bypass capacitor tacked on in strategic locations can work wonders. Are you sure you used the correct 74xx parts for the buffer logic? The the letters in the middle, LS, S, ALS, HC, etc matter in many cases.