Cannot connect to database via TNS

Question

Hello!
I installed XE with default settings and have some trouble. I cannot connect to database via TNS. Two symptoms:
1. I can connect with SQLPLUS system/pwd (locally, without tns name input), but CANNOT connect with SQLPLUS system/pwd@EX (WITH TNS NAME input).
2. I cannot start Database Home Page.
How to avoid this problem? Any ideas?
DETAILS:
PC configuration: Win2k+SP4, 512Mb, Outpost Firewall (disabled!), No another Oracle products being installed.
TNSNAMES.ORA file:
************* BEGIN TNSNAMES *****************************************
XE =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = pz)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
ORACLR_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
(CONNECT_DATA =
(SID = CLRExtProc)
(PRESENTATION = RO)
************* END OF TNSNAMES *****************************************
Listener status:
************* BEGIN STATUS *****************************************
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC_FOR_XE)))
STATUS of the LISTENER
Alias LISTENER
Version TNSLSNR for 32-bit Windows: Version 10.2.0.1.0 - Prod
ction
Start Date 22-MAR-2006 17:27:15
Uptime 0 days 1 hr. 8 min. 53 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Default Service XE
Listener Parameter File D:\oracle\ora10xe\app\oracle\product\10.2.0\server\ne
work\admin\listener.ora
Listener Log File D:\oracle\ora10xe\app\oracle\product\10.2.0\server\ne
work\log\listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(PIPENAME=\\.\pipe\EXTPROC_FOR_XEipc)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=pz)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=8080))(Presentation
HTTP)(Session=RAW))
Services Summary...
Service "CLRExtProc" has 1 instance(s).
Instance "CLRExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "XEXDB" has 1 instance(s).
Instance "xe", status READY, has 1 handler(s) for this service...
Service "XE_XPT" has 1 instance(s).
Instance "xe", status READY, has 1 handler(s) for this service...
Service "xe" has 1 instance(s).
Instance "xe", status READY, has 1 handler(s) for this service...
The command completed successfully
************* END OF STATUS *****************************************
NETSTAT -an results:
************* BEGIN NETSTAT *****************************************
Proto Local Address Foreign Address State
TCP 0.0.0.0:1521 0.0.0.0:0 LISTENING
TCP 0.0.0.0:2298 0.0.0.0:0 LISTENING
TCP 127.0.0.1:2455 127.0.0.1:8080 ESTABLISHED
TCP 127.0.0.1:8080 0.0.0.0:0 LISTENING
TCP 127.0.0.1:8080 127.0.0.1:2382 CLOSE_WAIT
TCP 127.0.0.1:8080 127.0.0.1:2455 ESTABLISHED
TCP 192.168.200.49:1521 192.168.200.49:2298 ESTABLISHED
TCP 192.168.200.49:2298 192.168.200.49:1521 ESTABLISHED
<truncated>
************* END OF NETSTAT *****************************************
I found following error in SQLNET.LOG:
*************** START LOG *********************************************
Fatal NI connect error 12570, connecting to:
(LOCAL=NO)
VERSION INFORMATION:
     TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
     Oracle Bequeath NT Protocol Adapter for 32-bit Windows: Version 10.2.0.1.0 - Production
     Windows NT TCP/IP NT Protocol Adapter for 32-bit Windows: Version 10.2.0.1.0 - Production
Time: 22-MAR-2006 17:28:59
Tracing not turned on.
Tns error struct:
ns main err code: 12570
TNS-12570: TNS:packet reader failure
ns secondary err code: 12560
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0
*************** END OF LOG *******************************************

Answer 1

I successfully connect with XE client to another Oracle databases from LAN, including 8i and 9i databases.
But cannot connect from another machines to my XE.