Hi. I have been using my arduino board lately and all of the sudden it won't turn on, be recognized by the computer, and the green ON LED is obviously not flashing. Is there any hope for it or no, and for future reference, what the heck could have caused this?!?!?!? I have tried both of my USB cables and I have came to a conclusion it is definitely the board. 
THANK YOU,
Ethan 
It is possible you had a short in your project and tripped the polyfuse, which is included in the design of several models of Arduino boards to protect your board and the computer. I have not tripped one before, but what I read online it takes from several hours to several days to reset, and resets automatically. So I would advise wait until tomorrow or the next day and try it again. I recommend disconnecting it from your project's circuitry or shields when trying it again. And finally, I recommend getting another Arduino if this is your only one, because having another Arduino handy is, well, handy. And the prices of derivative or clone boards are very affordable in most places.
Thank you so much @dmjlambert !! It was yesterday so I will test it now! Thx
Ethan
I think that did happen but now something weird is happening. On my breadboard I have set up a system with three LEDs and three buttons. Everything works perfectly fine except when I touch the wire to the ground pin. One before I touch the GND pin and one after I touch the GND. Basically, before the ON LED is green but after everything stops lighting up. How do I post pictures?
Also... One final thing. It might not necessarily be just the GND pin, for when I put the wire attached to the three LEDs to the GND FIRST, it does not stop working; but when i attach the wire connected to the three buttons to the 5V pin, then it stops working. In conclusion, it is something that when one of the two(GND from LEDs or 5V from buttons) is connected on either side, the other cannot be used. I REALLY DON'T KNOW... lol THANK YOU!!!
Ethan