--- a/urllib2_kerberos.py
+++ b/urllib2_kerberos.py
@@ -62,8 +62,8 @@ class AbstractKerberosAuthHandler:
         host = req.get_host()
         log.debug("req.get_host() returned %s" % host)

-        tail, sep, head = host.rpartition(':')
-        domain = tail if tail else head
+        cindex = host.rfind(':')
+        domain = (cindex == -1) and host or host[:cindex]

         result, self.context = k.authGSSClientInit("HTTP@%s" % domain)

@@ -130,15 +130,15 @@ class AbstractKerberosAuthHandler:
             if resp.getcode() != 200:
                 self.authenticate_server(resp.info())

+            self.clean_context()
+            self.retried = 0
             return resp

         except k.GSSError, e:
             log.critical("GSSAPI Error: %s/%s" % (e[0][0], e[1][0]))
-            return None
-
-        finally:
             self.clean_context()
             self.retried = 0
+            return None

 class ProxyKerberosAuthHandler(u2.BaseHandler, AbstractKerberosAuthHandler):
     """Kerberos Negotiation handler for HTTP proxy auth