Here's the scenario:
We have a SPD custom workflow that is using the "collect data from user" action. So we have a number of fields in a Task list that the user needs to input.
We are customizing the InfoPath form for that Task list, and want to submit the data both back to the task list (as the normal Submit action would do) and to a MSSQL database (we have written a web service for this).
I have added the web service as an additional data connection and I have mapped the fields to the web service parameters. I can test the submit action in the InfoPath preview and can see that the data is successfully inserted into the database, so the web service connection works correctly.
To get the web service working (it is hosted on a machine other than the SharePoint server) I have had to enable cross-domain access for form templates in Central Administration.
Here is where I am running out of ideas. If I leave the InfoPath form as is, and don't convert the web service data connection to a UDCX connection, I get an error about restricting cross-domain connections. However, when I convert the connection to a UDCX connection in InfoPath, I can no longer submit the form because I get an InfoPath form saying the web service is returning an HTTP 400 error.
Does anyone have any ideas on what can be done here? I am at my wits' end on this one.