“An error occurred accessing a data source.”
Generally it is due to database or webservice connection. If you are getting this error
1. First make sure the user has sufficient permission to access the database/web service.
2. In infopath ->Tools ->Form Options ->Security and trust ->Uncheck “Automatically determine security level” (If database/webservice is on same domain then select domain else select proper option)
3. Convert your data connection in udcx file.
For this, create a data connection library in MOSS.
Now open infopath form -> tools->Data connections
Select data connection and click on “Convert… “ button.
Give data connection library url with file name.
4. Now open Data Connection Library and Right click on udcx file -> “Approve/Reject” -> Select Approve and click OK.
5. Goto Central Administration ->Application Management->configure infopath form services->
“Allow user form templates to use authentication information contained in data connection files” option must be checked.
If your database/web service is placed on another domain then you need to check next option “Allow cross-domain data access for user form templates that use connection settings in a data connection file”.
Hope, It helps!!!