Event Type: Error
Event Source: Microsoft Firewall Client 2004
Event Category: None
Event ID: 1
Date:  10/8/2005
Time:  8:28:09 PM
User:  N/A
Description:
Application [svchost.exe]. Authentication failed. The user credentials were not accepted by ISA Server.  Verify that the user account running this application has the required permissions.

Solution:

Ensure that UDP and TCP port 1745 from client to server access is enabled (Access rule).