I have a program that our customers have been using for years without
this problem occurring. I use LogonUser to verify the id and password.
I use LOGON32_LOGON_NETWORK to avoid any long delays. In this
particular case, LogonUser returns 0 and GetLastError is immediately
called to get the failure code. Unfortunately, it returns 0 so I have
no idea what LogonUser is unhappy about.

if (!LogonUser(work_entry.clntData.posid.szUser,
		szDomain,
		GetUserPassword(work_entry.clntData.posid.szUser),
		LOGON32_LOGON_NETWORK,	 // wm20061108 - speed up the logon process
		LOGON32_PROVIDER_DEFAULT,
		&hUser)) {
	int ret = GetLastError();
	GetErrorMessage(errmsg);
	nSts[0] = DEF_RTC_SECURITY;
	nSts[1] = DEF_RC_NOSUCHUSER;
	OASIDailyLog() << ZTimeStamp() << "ERROR: LogonUser failed for user "
				<< work_entry.clntData.posid.szUser << " (" << errmsg << ")" <<
endl;
	if (hUser)
		CloseHandle(hUser);
	return FALSE;
}

I have seen in the documentation where SE_TCB_NAME is supposed to be
set for the user id when using LOGON32_LOGON_NETWORK on Windows 2000
but this has never been a problem before and, in this instance, the
user is running 2003 Server. I would greatly appreciate it if anyone
could shed some light on this for me.