Theres a error of "Cannot open connection" in the following lines

<property name="hibernate.connection.driver_class">com.microsoft.jdbc.sqlserver.SQLServerDriver</property>
<property name="hibernate.connection.url">jdbc:microsoft:sqlserver:@192.168.0.64:1433/hibernatetutorial</property>


I have installed Service Pack 3 for SQL Server.
Everything is properly configured infact the connection was also establishing, but suddenly it start giving Error "Cannot open connection".

Kindly reply me itz urgent

Thanks in advance...