ADO - Cursor Types

I know different cursor types offer different functionality, the most annoying one beng lack of recordcount in some, but when I try to run this query: -

Code:

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SELECT DISTINCT *
FROM Ticket
WHERE [AgtTNumber] IN
        (SELECT [AgtTNumber]
      FROM [Ticket] AS Tmp
      GROUP BY [AgtTNumber], [BorisBooking],
          [BorisOpLine]
      HAVING COUNT(*) = 1 AND
          [BorisBooking] <> [Ticket].[BorisBooking] AND
          [BorisOpLine] <> [Ticket].[BorisOpLine]) AND
    Reconciled = 0
ORDER BY [AgtTNumber], [BorisBooking], [BorisOpLine];

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with a Keyset, I get told that 'Object or Provider is not capable of performing the requested operation' but using a Dynamic crsor it works fine

why is this???