If we have more then one dataset in our report, or add more dataset in a report, we get this type of error message. To solve it :
If its a table, List, or Matrix : Right click the object (make sure the whole object is selected and click properties. if properties slides out Scroll down to “Dataset Name”, there should be a drop down which all the datasets in your report. Select the one you are grabbing you attributes from.
IF the properties box opens up for the table/matrix/list , then you should see (3 textboxes down) “Dataset Name”. if its empty or has something in it…i would click the dropdown anyways, and make sure the right dataset it selected.