amit,
Your data in the DATETIME format may be out of the boundries of SMALLDATETIME.
DATETIME
January 1, 1753 through December 31, 9999
SMALLDATETIME
January 1, 1900 through June 6, 2079
Microsoft SQL Server Books online Topic: datetime and smalldate
Happy T-SQLing
"Key"
MCITP: DBA, MCSE, MCTS: SQL 2005, OCP