I can confirm this after upgrading from JRS 5.5 to JRS 5.6. To repro: From the home screen, select Create Domain.At the Add New Domain screen, choose a Save Location (e.g., /public/Samples/Domains).At the Add New Domain screen, select a Data Source (e.g., /public/Samples/Data_Sources/FoodmartDataSource).Select a schema (e.g., public)Select a table (e.g., public_account)Click the Display tab.From the Resources list, select a table (e.g., public_account), and move it to the Sets and Items list.At this point the OK button is enabled.Click the OK button and observe the errror noted by the original poster.Please let me know how to better debug this issue. Thanks