It is common for InfoPath Form to utilize web services as secondary data sources. Normally there is no problem if InfoPath forms are opened in a InfoPath Client application, but problems occur when InfoPath forms are opened in browser, i,e, using InfoPath Form Service.
There are 2 options to workaround brows-enabled Form with web services: one is to set form "Full Trust":
This option will require Administrator-approved publishing option.
and the other is to convert data sources into data connection:
This option will allow form trust at Domain level, and with other publishing options available, but this option will require "Cross-Domain Access" checked for InfoPath Service from Central Admin:
For browser-enabled Infopath form, web services are called from sharepoint server, sometimes the network communication problem between sharepoint server and web service server can block services for browser-enabled forms, but could have no impact when InfoPath Client applications open the same form, or have no impact on web service configuration at design time.
