Writes letters often double

I ordered and tested this keyboard and unfortunately have to say that the keyboard is often in an attack outputs two letters. I use Windows7 Professional 32bit. The receiver I have applied to the most diverse places, but this has brought nothing. The mouse works flawlessly. The design of the keyboard and mouse is Top. However, you can use a keyboard that does not work properly, not really start something. I write in this moment an email to Cherry, to find out if the have a solution. Otherwise, I have to return the keypad unfortunately.
I have the keyboard already been changed once. However, the error occurred in both keyboards.
I admit at this point only one star because the product is not to be used in my eyes.