The problem: When accessing a SQL table or view from a browser enabled InfoPath Form gives you an error Data adapter failed during OnLoad
This happens when using a dataconnection to a SQL server using a .udx file.
To solve this you need to have Enable embedded SQL authentication checked. Also if your SQL runs on another server you need cross domain acces. So make sure that Allow Cross-domain data access for User Form Templates is checked.
Change these settings in Central Administration/Configure InfoPath Forms Services
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