I know there are a lot of different threads about this error but I never saw it related to my particular problem:
When I try to add a form template (using the Infopath Integration wizard) containing a UDCX-based Data Connection, I get this error. It also occurs when I modify a form template already included in my K2 project (using "design" in the IP Integration wizard) and convert one of the existing Data Connections.
Is it impossible to call (custom) web services in K2-enabled Infopath web forms?
Please remember to change the thread status when a valid answer has been given