Ok guys got the same pb :
Some times the "TCPTUNNEL" or "Microsoft Loopback Adapter" got bugs with XP sp2.
Impossible to connect or invalid password.
I got 1 solution to resolve this bug.
Just restart "microsoft loopback adapter" (just desactivate and reactivate when u try login with l2walker during this message :
01:39:04 »¶Ó*ʹÓÃÐÐÕß¡£Ö÷Ò³

01:39:04 Link LoginServer Succeed.
01:39:05 Password does not match this account. Confirm your account information and log in again later.
01:39:05 ->Login LoginServer Fail.
after this u can log easly :
13:53:52 »¶Ó*ʹÓÃÐÐÕß¡£Ö÷Ò³

13:53:52 Link LoginServer Succeed.
13:53:55 Login LoginServer Succeed.
13:54:00 Link GameServer Succeed.
13:54:06 ->Enter Char[5].
thx u all for posting and helping others in this great forum.