Having some trouble with 2 of 3 r-box's.

1 started acting up yesterday, the hash rate started dropping and after various restarts to cgminer and the computer, the pc eventually stopped detecting it.  The fan and red lights come on with the power cable, but nothing after plugging in the usb cable. 

It also appears that a chip to the right of the usb port is getting really hot, the pictures show this as the SILABS chip.

Tonight the 2nd one is doing the same thing.

Anyone have any thoughts or ideas on this?