Database "operation not applicable" error

When refreshing data after posting I occasionally get an error, "operation
not applicable". This seems to occur only in circumstances where there are
TDBMemo components on the form and when data has been added to one of these
components. I am using an Interbase database with Blob Text fields. The
refresh that I am speaking about is a simple Query.Close followed by a
Query.Open. I do this in order to refresh the data in a grid on the form.
Any help with this would be greatly appreciated.

Elliott Mehrbach