[avr-gcc-list] at90usb1287- usb unplugging problem

[P.Arun]

Hi friends,
      I use STK525 kit for the development of a HID keyboard. Actually, 
i has two STK525 kits. one is older one and another is recently bought 
one. I had written the code such that when the code is running with usb 
cable unplugged, an LED will blink to indicate that usb is unplugged  
and the LED will begin to glow when we plug in usb cable. This code 
works in older kit. but when I try the same code for newer kit, it works 
asusual as far as other aspects concerned. but when  I unplug the usb 
cable, the target board goes to sleep mode  
           
          when I again plug in the usb cable, the microcontroller get 
resetted and it works as usual.
 can somebody explains me, why the microcontroller goes to sleep mode 
in the new stk525 kit when the usb is unplugged?. The version of new 
stk525 kit is V.1.01.

Please help me.

thanks in advance,
Arun.