If you've installed ISA 2004 SP3 or the recently-released ISA 2006 Supportability Update, you may have noticed missing status codes:
As you may guess from the Filter information field, the status should say "12217 The request was rejected by the HTTP filter. Contact your ISA Server administrator."
This happens when you're looking at logs on a management-only computer (on ISA2004, also on a CSS computer). The status descriptions are stored in the file mspmsg.dll, which is not installed in these cases.
The solution is simple: Just copy mspmsg.dll from an ISA Server computer to your management computer (in the ISA installation directory, typically C:\Program Files\Microsoft ISA Server). Be sure to copy from the a computer with the same version, SP and patch level as your management computer! Once copied, move to another screen, say Firewall Policy, and then back to the Monitoring screen - the status descriptions show appear once again.
Edit - Additional symptoms of the same issue, and with the same workaround:
-Jonathan BarnerISA Server Sustained Engineering Team
Security Microsoft and Novell Open Interoperability Lab http://www.microsoft.com/presspass/press/2007/sep07/09-11MSNovellLabsPR.mspx