I am getting the error when configuring a Call Web Service task. The credentials that I am supplying in the configuration of the task have access through the proxy and to the web service. If I paste the URL of the web service into a browser, the call works and I get the expected response, just not from the Call Web Service task.
I tried using the Web Request Task as well and I get the same result.
Is there somewhere I need to set up separate credentials that the Call Web Service task will use for proxy access?
I was unable to find a record of the webservice call in my proxy log so I assumed that no call was being made. I added my site to the 'Pass through' group of URLs and the error went away. I would still love to know what credentials the proxy sees when the call is made by a workflow, but I guess that is a question for the proxy support team.
The request is executed with the credentials that you provide when configuring the web request or call web service action. But the request is executed from the SharePoint server. So your SharePoint server should be well configured to access the proxy server. Also you need to configure the proxy in the web.config of the SharePoint web applications (in IIS). If your workflow is executed by a Schedule, then you should configure the proxy in the OWSTIMER.EXE.config in the BIN folder of the SharePoint installation folder.
Hope this helps