DataSet Works... DataTable Doesn't... (ODBC)

I have a longstanding problem where Stored Procedures or complex T-SQL called from VB.NET will not populate a DataTable object, but will work fine with a DataSet.  For example:
    'oConn is defined elsewhere...
        Dim sErr as String = ""
        Dim dt As New DataTable
        If Not oConn Is Nothing Then
            Try
                Dim sSQL as String = "select 1"
                Dim oCommand As New OdbcDataAdapter(sSQL, oConn)
                oCommand.Fill(dt)
            Catch ex As Exception
                sErr = "Database Error: " & ex.Message
            Finally
                sqlCloseConnection(oConn)
            End Try
        End If

this works fine and my dt DataTable object gets one row.  However using this as the SQL:
                Dim sSQL as String = "declare @foo table(mycol integer);insert @foo select 1;select mycol from @foo;"

does not work.   It executes with no errors, but the DataTable has no rows.  Finally, if I replace the DataTable with:
                Dim ds as DataSet
I can then get the data in ds.Tables(0) no problem.
So, if the results of the sql are a single result table being put at index 0 of a DataSet, why are they not being put in a single DataTable?
When a sql is a simple select statement it always works directly to a DataTable.  Only when it's a SP or sql with some logic does it require the DataSet approach.  This is a reporting utility so I need to standardize the code though the sql will be dynamic.

 
Any ideas?