ORA-12535: TNS:Operation timed out.

 Hi
I am getting the error "ORA-12535: TNS:Operation timed out."
While connecting to one of the database from client. Below is the tnsnames entry to connect to database.

TST1.GCC.COM =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST =xx.xxx.xxx.yyy)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SID = TST1)
      (SERVER = DEDICATED)
    )
  )

I am able to perform a successfull tnsping to the database with the same entry.
From the same client system I am able to connect another databases.