Error using Mechanize to open and submit form

I am getting the following error trying to use mechanize to open and submit a web page:

Module /usr/local/Plone/zeocluster/parts/client1/Extensions/authorizenet2.py, line 25, in chargeHash
Module mechanize._mechanize, line 203, in open
Module mechanize._mechanize, line 230, in _mech_open
Module mechanize._opener, line 193, in open
Module mechanize._urllib2_fork, line 344, in _open
Module mechanize._urllib2_fork, line 332, in _call_chain
Module mechanize._urllib2_fork, line 1170, in https_open
Module mechanize._urllib2_fork, line 1118, in do_open
URLError:

Here is my code:

def chargeHash(self,login,seq,amount,trankey,emplid,url,formname):
timestamp=str(int(time.time()))
msg = '^'+login+seq+timestamp+amount+'^'
msg = login+"^"+seq+"^"+timestamp+"^"+amount+"^"+"USD"
fingerprint = hmac.new(trankey,msg).hexdigest()
fingerprint=fingerprint.upper()
dict={'hash':fingerprint,'ts':timestamp}
br=mechanize.Browser()
br.set_handle_robots(False)
br.open(url)
br.select_form(formname)
br.form['x_fp_hash']=fingerprint
br.form['x_fp_timestamp']=timestamp
req=br.submit()
return

Use pdb and inspect the error.