"How to Block Dangerous Instant Messengers Using ISA Server" written by Dr. Shinder could missguide the unexperienced administrator. If you act according to the article, go to firewall client configuration, then add new application, then choose Disable, and finally enter value "1"; you will disable the firewall client when that application is used. You are not going to disable the application to go through the firewall.
Other Dr. Shinder's articles really helped me a lot. This is probably just a glitch.
Precisely! If you make the change in the mspclnt.ini file, and the machine is configured as a Firewall client, the application will not work, at least not when connecting to the Internet. However, it will still connect to LAT based hosts, but I don't think many people are concerned about that