Help! Arduino Leonardo Installation Problem

I Want to make a WebServer with Webduino Library , but i have 2 Arduinos , one is UNO , Another is Leonardo.
the UNO is Other purpuses.
the Leonardo , i Connected to the computer , UNO is Com3 , Leonardo is COM6.
but , Usually Leonardo is COM6 , but if in Uploading.
the :

Arduino Leonardo (COM6)

is Change to :

Arduino Leonardo bootloader (COM7)

in the Windows Device Manager.

Arduino says : Upload Done.
but Leonardo is No response.

Why?

OS : Windows 8.1 Pro

have similar problem but mine is i am using mac with 10.9.3 and i can not communicate with the leonardo at all. tried all mean. they say that the new os made its own driver and overriding the one that comes with the arduino package. :disappointed_relieved: