I just received a broken Melzi and fixed it up, after replacing all the stepper drivers and adding a new 5v regulator all was good except the X dir pin (which goes directly to the micro) it seems it got burned after my friend connected the power in reverse.
So, if you have had any wiring issues, the problem may be similar to the above.... If you are running pre-installed firmware, then the chances are that the fuse settings are already correct...... as you wouldn't normally have to change this if the board has been flashed with the sangulino bootloader as supplied with the Marlin firmware.
You can try re-flashing your boot loader with an isp programmer, I used a UsbAsp programmer off ebay for less than £10, the UsbtinyIsp will give errors (but does work) and using an arduino as isp didnt work at all.
So, if you have had any wiring issues, the problem may be similar to the above.... If you are running pre-installed firmware, then the chances are that the fuse settings are already correct...... as you wouldn't normally have to change this if the board has been flashed with the sangulino bootloader as supplied with the Marlin firmware.
You can try re-flashing your boot loader with an isp programmer, I used a UsbAsp programmer off ebay for less than £10, the UsbtinyIsp will give errors (but does work) and using an arduino as isp didnt work at all.