AMON severly slows down file access

I've been using NOD32 for eight months with no problems. As part of my work once every month or so I run a program that reads every file in a directory of 16,000 or so files. It normally takes around 15 minutes. When I ran it today, it took over three hours.

Looking at the Windows Task Manager, the "System" process was consuming 50% of my CPU (I have a dual-core system). Using the Sysinternals process explorer, I further narrowed it down to the amon.sys thread within the System process.

I turned off AMON temporarily and re-ran my program, and it finished in its usual 15 minute time.

I'm running WinXP SP2 with automatic updates, and I just got the latest update last night (June 12-13). I also have NOD32 updating automatically.

Any guesses as to why AMON is suddenly slowing down file access?

 

Are those files executables/dlls or another type?

 

They are not executables, but they are binary files. They are form files for an imaging engine that produces real estate docs. Their file name suffix is ".fdf", which is unfortunately shared by Adobe form files.