I tried all the steps that you gived to me:
Connect the MKii to your PC. Install the drivers for it that are in the IDE folder.
My path is: c:/arduino-1.0.5/hardware/tools/avr/utils/libusb/bin
Once installed and appearing correctly in Device Manager, start the IDE.
Select Files:Preference, and check the Verbose output boxes.
Connect the MKii to the ICSP header on your board. Red light will be on.
Power the board - MKii only monitors the power, it will not provide it. Green light should turn on.
Select Tools: Programmer: AVR ISP MKii
Select Tools: Burn Bootloader. Green light in MKii will flash for a while, when it goes steady green again the bootloader should be installed.
Read the messages at the bottom of the IDE, there should be no error messages.
But I have only an error messege: "usbdev_open() : did not find eny usb device "usb" "