Experienced a very strang issue with a query after upgrading to SQL Server 2008 from 2005. A query that took less than one second on SQL 2005 ended up taking 27 seconds on SQL Server 2008.
Query that selects data and one of the columns in the select list belonged to a full text index. If this column is not in the select list, the query runs in under one second.
Removing the full text index did not make a difference
Changing the data type from nvarchar(max) to nvarchar(3000) did not make a difference
adding a where filter of column != '' worked
Not sure why this happened and only in SQL 2008 but not in 2005 but if you are seeing the same issue, I hope this article helps.