Issues with SVN and GNU Diff Utils

I'm attempting to get a diff through the Win32 GNU Diff Utils and I'm
running into weird issues.

The following command:
C:\Projects\Eastgate>svn diff -c 187 --diff-cmd="c:\Program Files
(x86)\GnuWin32\bin\diff.exe"

Always returns this:
Index: src/file.py
===================================================================
svn: E200012: 'c:\Program Files (x86)\GnuWin32\bin\diff.exe' returned 2
svn: E175002: Error reading spooled REPORT request response

In this case, the file was newly added in the changeset I'm getting the
diff for.

What's going on here? Is there an easy way to fix this?

--
Jeff