libusb mkii digital signature

got a Mkii, wen tot load bootloader through IDE, but windows won't allow me to use the arduino libusb drivers because of an invalid digital signature.

What gives?

trying on OSX...did the file mod in programmers.txt to change it from USB to serial, and it just sits there for infinite time saying "burning bootloader, this may take a minute". LED doesn't light on the mkii.