Prepared Statement Vs. Management Studio

Hello Folks,

I have a problem with a prepared statement against SS2005 SP2 that I do not fully understand. I have a query that is prepared and executed from a java application that looks similar to this:

SELECT TOP 1 str.ID FROM bigtable1 big1
LEFT OUTER JOIN bigtable2 big2
ON (big1.ID = big2.ID)
LEFT OUTER JOIN htable h ON (big2.HID = h.HID AND h.DIRECTSW=1)
WHERE big1.ID IN (SELECT ID FROM ltable WHERE LID IN(SELECT
LID FROM LAS WHERE LASID = ? )) AND big2.COMPLID <> 2 AND big2.COMPLID <> 3
AND ISNULL(big2.date1, big2.date2) BETWEEN ? AND ?

When run as a prepared statement this runs in about 27 seconds. When run under the query component of Management Studio it runs in about 1 second. Before each run I am clearing the buffers and the prepared statement cache. When running these I have looked at the execution plan from profiler and they both look the same. If I change the

WHERE big1.ID IN (SELECT ID FROM ltable WHERE LID IN(SELECT
LID FROM LAS WHERE LASID = ? ))

to INNER JOIN it runs ~1 second in both environments.

Any pointers would be welcome to explain the disrepency.

Thanks, Mark