How to convert NTEXT to NVARCHAR(MAX)Posted: April 30, 2012
John Conwell has a post about the issues associated with the conversion of NTEXT to NVARCHAR(max) in SQL Server 2005 back in 2008. http://geekswithblogs.net/johnsPerfBlog/archive/2008/04/16/ntext-vs-nvarcharmax-in-sql-2005.aspx
The observation and fix he found in SQL Server 2005 is still true in SQL Server 2008 and SQL Server 2012.
Here is the the tak aways from his post which still apply to SQL Server 2008/2012:
You need to do an UPDATE to the column which is converted from ntext to nvarchar(max) after the alter table alter column statement.
ALTER TABLE testTable ALTER COLUMN testText NVARCHAR(MAX) null
UPDATE testTable SET testText = testText