Secondary data connection using sql server in Infopath,while customizing sharepoint list is throwing

Hi,

I created a custom list in Sharepoint 2010 publishing site. In the list, I edited the form using Infopath. In the Infopath 2010, I created a secondary data connection by selecting the database option. Selected SQL Server option. Gave the username and password
option. I got the list of tables in that database, selected the table and created the data connection. In the form, i used the fields from the secondary connection to fill few of the fields, using the rules. I didnt check the preview. I published
the form to the list. When i tried to open the form in the sharepoint list, by clicking Add Item, I am getting error. The error was related to correlation error.

I tried deleting the secondary connection, made a external list, and connected this external list as secondary data connection. Now when i opened the page in the site, everything is working.

What could be wrong. Is it not possible to use sql server as database in the custom list for secondary data connection?

Also, in the Infopath options, I was not able to see the security tab, when opened using the sharepoint list. Is this a permission issue. If yes, how to make the page in full trust, while customizing through sharepoint list.

Thank you

Hi Clayton,Thank you very much for the reply.