Is this in DEV or PROD system...
Did you make any changes to the datasource (like adding or removing fields)?
You will get this type of error when the PSA Table is corrupted.
Go to the PSA table directly (u will see this at the top of the pop-up when you do Manage Datasource) and check if it is active and there is any data in the table....
If it is dev, delete infopack, replicate the datasource again...activate it and load it again