Subtle problems of these kinds may require saintly patience to work through, because you do not usually get very good feedback from SharePoint web services as to the underlying reason for the failure. The tools found to be helpful include the following:
Wire-level debugging. In your logging,properties file, add "log4j.logger.org.apache.http=DEBUG" and/or "log4j.logger.org.apache.http.wire=DEBUG", and restart the appropriate service to make the logging take effect. For versions of ManifoldCF after 2.7, you will need to edit logging.xml instead, and add the following to your loggers section:
<Logger name="log4j.logger.org.apache.http" level="DEBUG" additivity="false"><Appender-ref ref="MyFile" level="DEBUG" /></Logger> <Logger name="log4j.logger.org.apache.http.wire" level="DEBUG" additivity="false"><Appender-ref ref="MyFile" level="DEBUG" /></Logger>
- Windows event logs. Depending on the problem, the security log might be appropriate; for other problems, the application log would be better.
- Packet captures, using tcpdump and/or Wireshark. This helps finding the causes for unexpected redirections, or other http-gated issues.