It turns out that, while I've been running test_core for 32-bit Python
on Win64, I *haven't* been running it for 64-bit Python on Win64
(because I didn't have 64-bit Pygame or Numpy installed (now fixed)).
Test core did fail due to the use of a Python int for an IntConstant
where the value was 0xffffffff, (Python's int is apparently 32-bit on
64-bit Python, sigh).  With that fixed (in bzr head), running: Tests.test_fbo

*does* run correctly on a Win64 machine with 64-bit Python, Pygame and
Numpy.  That is, I am using:

         fbo = glGenFramebuffers(1)

and getting the expected frame buffer, then rendering something into it,
then rendering a quad with that texture on it.

Weird thing is, you couldn't even *import* PyOpenGL on 64-bit Python...
so either it got broken rather recently or something fishy is occurring.

That's weird, I've been using PyOpenGL for Python 64 bits on Windows 64 bits for some time (at least a year). I've always been using Chris Gohlke's build.