I've done some quick research into this, and it turns out that while it's possible to obtain a timestamp in Windows to 100-nanosecond accuracy, the value returned is only updated once each timer tick[1], or about once every 16 milliseconds.

It'd seem that that update mechanism is the "magic barrier" you see. Cambridge University offer a solution to this, written in C++ - but whether that'd help you any I don't know :)

1. http://www.cl.cam.ac.uk/users/kw217/useful/win32time.html