InfoPath Dev

Simple sharepoint list being customised in InfoPath.
2 dropdowns. I is a lookup to a list. The second is a data connection from list values based on the selection made in the first dropdown.
Everything is fine except when the 2nd selection is made the form complains that only integer values are allowed.
Should be no integers involved, both dropdowns are text values. When I set the data connection for the second drop down I only get a single column to choose from (which is the column we need).
So fetch field1 from list2 where list2.field2 (secondary data connection) = main.fieldname

All fine except for this validation issue.
 

Actually, in a SharePoint list form, a drop down is usually a lookup column in the list, I think ... So I'd expect the control wants the ID for the item you are choosing. What is your drop down set to in the drop down properties? I think the value should be the list item's ID. Can you give that a try?

 Hope the images explain, first one is the InfoPath setup that makes the cascade. Second is the list column definition in sharepoint.
I've done this a couple of times in the past but don't remember striking this issue.

https://onedrive.live.com/redir?resid=c18b04d5bb544db4!5648&authkey=!AESwt8K60w79bCw&v=3&ithint=photo%2cPNG

https://onedrive.live.com/redir?resid=c18b04d5bb544db4!5647&authkey=!AEMNFdf_uKv9QGE&v=3&ithint=photo%2cPNG

I tried to inset them as images but they just appear as broken images when I do 

 Should add that the list (that this InfoPath serves) has 2 lookups, both drop downs and both involved in the cascading bit.
The first dropdown "building" expects the text value from the drop down selection but the second dropdown (which is initially populated based on the 1st DD selection) does not.
I can change the data connection to store the ID and it is ok then... but that is no good to the end user who need to see the text

This is a list form? What is displayed in the list when you change the drop down to use ID for the value and structure for the display?

 Solved it. Yep should have selected the value of ID.
The problem was that the only fields available to me under value and display were "."
After digging around I realised I had selected a field under "entries" rather than the sharepoint list node, so the other fields weren't available for me to set