We encounter this error in Microsoft Dynamics GP Report Writer. I experienced the same recently and here is the cause and resolution for the error.
If we have fields dragged to the far right of the report layout or presence of any unusual characters like #,*,+ in text fields of the layout, we may get this error.
Quite simple that drag the fields back to the left or remove them if this is due to dragging issue. If it is due to the special characters, remove them from those text fields and add the text back to the report.