FWX_E_NO_BACKLOG_PACKET_DROPPED – What does that mean?

If you find that ISA Server 2004/2006 is denying connections, seemingly for no particular reason, and logs the following error:

FWX_E_NO_BACKLOG_PACKET_DROPPED

…it simply means that ISA Server does not have enough resources to do the logging. Check the CPU and hardware utilization. Also see if your disks are fast enough.

A workaround would be to disable logging for “high-volume” rules like SMTP and DNS.