Win2K3 SP2 wan connection problem

There are 2 Win2K3 SP2 servers (A, B) separated by wan link. In server A,

there is a share called "mike". In server B, a "net use" command is issued

as follow:

net use w: \\server-A\mike

However, a bad result comes:

System error 1236 has occurred.

The network connection was aborted by the local system.

When commands (ping / tracert server-A), the outcome is ok.

When server-A was installed with no service pack or service pack 1, the "net

use" command succeeded.

Other information

The above problem only happens between Windows 2003. Other combinations,

such as

(Windows XP SP2 & Windows 2003 SP2),

(Windows 2000 SP4 & Windows 2003 SP2),

(Windows 2003 SP2 & Windows 2003 SP2 without wan connection)

have no problem.