Strange fix to -> TNS:listener received no CONNECT_DATA from client

[SA23]

We have got the client/server application. The server has an Oracle 8.0.6 database installed. The front end (client's end) is a java applet that resides on a server. This applet is accessed from the client machine using the link on the client's home site. Java applet has several parameters that are used to make a connection to an Oracle database: instance SID, username, port number. The server is properly set to listen for incoming Oracle connections.

Tnsnames.ora:
-------------
TEST.WORLD =
(DESCRIPTION =
(ADDRESS =
(PROTOCOL = TCP)
(HOST = TESTMACHINE)
(PORT = 1521)
)
(CONNECT_DATA = (SID = TESTDATABASE))
)

Listener.ora
------------
LISTENER =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = oracle.world))
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
(ADDRESS = (PROTOCOL = NMP)(SERVER = cho54)(PIPE = ORAPIPE))
(ADDRESS = (PROTOCOL = TCP)(HOST = TESTMACHINE)(PORT = 1521))
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = extproc)
(PROGRAM = extproc)
)
(SID_DESC =
(GLOBAL_DBNAME = TESTMACHINE)
(ORACLE_HOME = c:\orant)
(SID_NAME = TESTDATABASE)
)
)

The problem was that when connecting to the database from client machine using Netscape the following error was thrown:
java.sql.SQLException: Operation timed out.
When I looked into listener.log file on the server there was the following error message:
20-FEB-02 10:57:58 * 12502
TNS-12502: TNS:listener received no CONNECT_DATA from client

Then we tried to connect from the same client using Internet Explorer. Connection was successfully established. After this we tried to connect from the same client using Netscape again and... the connection was successfully established. So the problem was fixed.

Could you please explain to me this strange fix to the problem I described above.

Thank you very much.

SA23