I am working in a list which contains around 300 different fields. I have also added another list as second data connection. Everything is perfect at this stage and i am able to publish successfully. After that i have given a action rule as Set Field Value to copy fields from the second data connection to Main data connection. Now i am not able to save the form and publish the same. I am getting "SOAP error when publishing Infopath form to Sharepoint" without any further description. If i disable the rule, then its published successfully. Since the above rule is necessary to copy data, i cannot disable the rule. Kindly help me to fix this issue.
One possible problem maybe, the "Main Connection" is a receive data connection and so you are not able to change the values of this data.
Though you can create data connections that submit data to a list which you could use, you would just need to create another data connection that submits data to the same list as the "Main Connection".
Hope this helps!