All out of nowhere I was getting intermittent 2-3 seconds freezes in my FSX. I checked my system monitoring and noticed a certain exe file jumped to 2nd place every time the freeze was happening. It turns out that Microsoft Security Essentials is the culprit.

It is a CPU slogger, and the freezes went away immidately when I shut it down.

Just a heads up

 

 

You should exclude all FSX-related files from MSE realtime scanning.

 

Hifisim, RadarContact and a host of other addons install outside of the FSX root folder, so they need additional excludes, on top of your FSX folder exclude.