Did I break my new Arduino Leonardo Eth by restarting it?
You should be able to use my board detector sketch on one of your other Arduinos to check out the problem board. 

See also Have I bricked my Arduino Uno? Problems with uploading to board

Also my bootloader uploader sketch will reflash bootloaders on quite a few devices. I'm assuming that the "Arduino Leonardo Eth" has the same bootloader as the Leonardo.

Hmmm - I see that the "Arduino Leonardo Eth" is from Arduino.org, not Arduino.cc. The bootloader is probably slightly different. I'm really not an expert on what those boards use.



Before worrying too much, try the approach of holding down Reset and then uploading a sketch, letting go of Reset as the sketch starts to actually upload.



Comment by William Hilsum


  I didn't realise there was a difference between .org and .cc, and, I guess by using the leonardo template from .cc, I broke "something". The moment I downloaded the IDE from .org, &amp; uploaded with the eth template , it worked flawlessly. I guess there are some changes between leonardo and leonardo eth. I wanted an arduino with ethernet, so I didn't need a separate shield. No idea if I picked the right "side" after reading all the crap with cc vs org! 


That is very annoying that the split of the Arduino camps now produces a support nightmare for people who just want to use their virtually identical products, but have to go through this.

Thanks for the update.