DLL load failing under IIS

I'm attempting to run ViewVC 1.0.0 on IIS (Windows Server 2003) going against Subversion 1.3.0 with Python 2.3 (and the Subversion Python 1.3.0 bindings). 

When I run the url, 
http://localhost/viewvc/viewvc.cgi, I get the following output:

An Exception Has Occurred

Python Traceback

Traceback (most recent call last):
File "C:\Program Files\viewvc-1.0.0\lib\viewvc.py", line 3611, in main
request.run_viewvc()
File "C:\Program Files\viewvc- 1.0.0\lib\viewvc.py", line 253, in run_viewvc
import vclib.svn
File "C:\Program Files\viewvc-1.0.0\lib\vclib\svn\__init__.py", line 25, in ?
from svn import fs, repos, core, delta
File "C:\Python23\Lib\site-packages\svn\fs.py", line 19, in ?
from libsvn.fs import *
File "C:\Python23\Lib\site-packages\libsvn\fs.py", line 5, in ?
import _fs
ImportError: DLL load failed: Access is denied.

I don't see any security restrictions on the DLL -- it seems to have the same rights as 
python.exe. Any ideas what might be causing this?

Thanks,
t.g.