ExecuteReader requires an open and available Connection. The connection's current state is closed.

private static int GetMovieID(string MovieName)
		{

			int MovieID = 0;
			OleDbCommand com = new OleDbCommand("SELECT * FROM movies                        WHERE [movieName]='" + MovieName + "'",cn);
			OleDbDataReader dr = com.ExecuteReader();
			while (dr.Read())
			{
				MovieID = (int)dr["ID"];
			}
			return MovieID;
            
		}