Seems core.thread.Fiber is broken dmd windows 64-bit build

[Carl Sturtivant via Digitalmars-d-learn]

Please confirm or deny that this is a real bug, as its getting in 
the way of a genuine project. How should I proceed?

I'm working on a 64-bit Windows port of the following.
http://www.cs.arizona.edu/icon/
Here's the 32-bit Windows port.
http://www.cs.arizona.edu/icon/v95w.htm

Among other things I'm using D to implement Icon's coexpressions 
portably using core.thread.Fiber which works fine at 32 bits. 
They are implemented using pthreads on other platforms, though 
historically there used to be a platform dependent assembly code 
context switch, close to the way that core.thread.Fiber is 
implemented. The Fiber implementation is 20 times faster at 32 
bits.