c# 2003.net connection

[tselvaa]

I have problem with the connection in c#.net 2003. when I am trying to connect with sql 2005 server this error will appear.
An unhandled exception of type 'System.NullRef erenceException ' occurred in system.data.dll

Additional information: Object reference not set to an instance of an object.

but my connection string works with c#.net 2005. what is the problem with the environment?

my connection string is
string constring="Pers ist Security Info=False;User ID=sa;Initial Catalog=DFNEWDB ;Data Source='TSELVAA \\SQL2005'; Packet Size=4096;Works tation ID='TSELVAA'";
SqlConnection con =new SqlConnection (constring);
con.Open ();

[Plater]

Did .NET1.1 event have the SqlConnection class? I was pretty sure you used to have to use the OLE stuff?