I've created a custom BCD for SharePoint 2010. It works well, i can create a list, view all the items, click on an item and view it.
I am now adding this to a list as an External Data column. The column adds, and the picker works, I can see all that I need. When I select one of the items, however it errors. The field value shows the BCS ID, __bk82000300030003000300030003006300530063009300, and the error below
No exact match was found. Click the item(s) that did not resolve for more options. You can also use Select button to choose External Data.