getting an HTTP Error 500 on a form post

[iBlaine]

I'm hoping someone here can answer my problem - I'm getting a 500
error when I run this code.  What it should do is setup cookies, log
in, then post a file to a form.  The problem is it throws an exception
at ClientCookie.urlopen(form.click()).  The webserver hosting the form
is fine, the python looks like it should work, I cant figure out how
to solve or debug this.

######### python code
# cookie handler
cookieJar = ClientCookie.CookieJar()
opener =
ClientCookie.build_opener(ClientCookie.HTTPCookieProcessor(cookieJar))
opener.addheaders = [("User-agent","Mozilla/5.0 (compatible)")]
ClientCookie.install_opener(opener)
fp = ClientCookie.urlopen("http://example.com/login.user")
forms = ClientForm.ParseResponse(fp)
fp.close()

# login
form = forms[0]
form["j_username"] = "bob" # use your userid
form["j_password"] = "1234" # use your password
fp = ClientCookie.urlopen(form.click())
fp.close()

# post new file
fp = ClientCookie.urlopen("http://example.com/form_page")
forms = ClientForm.ParseResponse(fp)
form = forms[0]
form["reportId"] = "4239"
form.add_file(open("/home/filename.xml"), "text/plain",
"filename.xml")
request = form.click()
fp = ClientCookie.urlopen(request)
fp.close()

########### error
Traceback (most recent call last):
  File "./old-import-xml.py", line 62, in upload_xml
    fp = ClientCookie.urlopen(request)
  File "/usr/lib/python2.5/site-packages/ClientCookie/
_urllib2_support.py", line 717, in urlopen
    return _opener.open(url, data)
  File "/usr/lib/python2.5/urllib2.py", line 387, in open
    response = meth(req, response)
  File "/usr/lib/python2.5/site-packages/ClientCookie/
_urllib2_support.py", line 391, in http_response
    "http", request, response, code, msg, hdrs)
  File "/usr/lib/python2.5/urllib2.py", line 425, in error
    return self._call_chain(*args)
  File "/usr/lib/python2.5/urllib2.py", line 360, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.5/urllib2.py", line 506, in
http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 500: Internal Server Error