Data type not valid

Hello:

I added a new field to my dataset query (at the end of the selected fields), which is clearly an integer field (it does a sum to get the value in the query), but SSRS is giving an error:

[rsInvalidExpressionDataType] The Value expression used in textrun ‘holdtime.Paragraphs[0].TextRuns[0]’ returned a data type that is not valid.

This would see like a bug--at first a tried using it in a formula and thought maybe that formula didn't like it so I added it as a new field by dragging and dropping. Is this a bug?

Thanks...