"unresolved external symbol" On Windows trying to call Panda3D's C++ API

I believe I might be seeing this issue, but I'm not sure:
http://trac.cython.org/cython_trac/ticket/106

I'm trying to compile a trivial Cython script that makes a call into
Panda3D's C++ API (Panda has a great python API, but it's easy to mix
with the C++ API, which seems like a nice job for Cython). It works
great for me on my Macs. On Windows, I have to use MSVC compiler (Form
Visual Studio 2008 Express) to work with Panda3D, and I get this error
when compiling:

   Creating library build\temp.win32-2.6\Release\testx.lib and object
build\temp
.win32-2.6\Release\testx.exp
testc.obj : error LNK2019: unresolved external symbol
"__declspec(dllimport) pub
lic: void __thiscall Geom::clear_cache(void)" (__imp_?
clear_cache <at> Geom <at>  <at> QAEXXZ)
referenced in function "struct _object * __cdecl
__pyx_pf_5testx_test(struct _ob
ject *,struct _object *)" (?
__pyx_pf_5testx_test <at>  <at> YAPAU_object <at>  <at> PAU1 <at> 0 <at> Z)
P:\CythonCXXTest\testc\testx.pyd : fatal error LNK1120: 1 unresolved
externals
error: command '"C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC
\BIN\link.
exe"' failed with exit status 1120

(Full output here: http://dpaste.com/238519/ )

My Cython source is:

cdef extern from "geom.h":
    cdef cppclass Geom:
        void clear_cache()

from panda3d.core import GeomVertexFormat,GeomVertexData
from panda3d.core import Geom as pGeom

print "Lets roll with C++"

format=GeomVertexFormat.getV3n3c4t2()
vdata=GeomVertexData('vdata', format, pGeom.UHStatic)
geom=pGeom(vdata)
v=geom.this

print "getting ptr"

cdef long dataPtr=v
cdef Geom* g=<Geom*>dataPtr

print "calling C++ method"

g.clear_cache()

print "done"

My setup.py:

import sys
import os

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext

# make setup do what we want,
# build extension modules in place
sys.argv.append('build_ext')
sys.argv.append('--inplace')

if os.name=='nt':
    include_dirs=[r'C:\Panda3D-1.7.0\include']
elif os.name=='posix':
    include_dirs=['/Developer/Panda3D/include/']
else:
    # Specify Panda3D include directory here for other systems
    include_dirs=['']

setup(
    name = 'Demos',
    ext_modules=[
    Extension("testx",
              sources=["testc.pyx"],
              language="c++",
              include_dirs=include_dirs,
              ),
    ],
    cmdclass = {'build_ext': build_ext},
)
print "Importing module"
from panda3d.core import Geom
import testx

I have tried the the Rectangles C++ sample with this setup on Windows,
and it did work fine, and if I remove the Call to panda's C++ API, my
code works fine, so I'm pretty sure the issue is linked to the C++
call.

If possible, I'd like to actually make this work on Windows. Any
suggestions for what to try would be greatly appreciated as I'm
completely out of ideas. I'd be happy to do further testing if it
would help resolve the issue, but I don't know what to try.

Thanks!