This error is returned in Visual Basic when trying to display a recordset based on a join between two feature class tables, in a Microsoft Hierarchical Flexgrid control:
Only one spatial column is supported in this operation()(<feature class name>)
The data grid control cannot support a recordset based on a join table that includes two shape (geometry) columns.
Construct a query for the recordset to join the two feature class tables that include, at most, only one shape (geometry) column.
Shape columns can be identified by their data type - ADO Data Type 204/205 (adVarBinary/adLongVarBinary).