Dual Core weird behaviour..

Hello everybody. I wanted to share a strange behaviour of my Core 2 Duo CPU with you and find any answers if possible.I run FSX on an Acer 9815 laptop with Core2Duo T7200 CPU, nVidia Geforce Go 7600 /256mb vram and 2 GB of Ram.I have also installed the Microsoft WinXP update KB896256 for dual core cpus, changed the registry value for PerfEnablePackageIdle to 1 and added the /usepmtimer switch in the boot.ini file (these settings helped a lot in FSX and other applications I tested).I run FSX with medium settings and constrained to 20fps. Everything works great for a 5-10 minutes period and then suddenly the fps drops to 2 or even 0.5! Then if I enter the map or pause FSX and minimize it for a sec then it changes back to normal fps and everything starts from the beginning. Sometimes it doesn't recover so I have to shut it down, reboot and start all over again.I made some tests and noticed that while running FSX the 1st cpu core works at its max while the 2nd at 2-15%. Of course I know that FSX doesn't use dual cores for now so that is something expected..The starange thing is that when the problem starts (drop of fps to 0.5) then even the 1st cpu works at 20%. It's like Windows don't let FSX use the 1st cpu either for an unknown reason.The KB896256 helped a bit but didn't fix the problem.Has anyone noticed this kind of behaviour?I'm not complaining for the overall thirst of FSX for system resources. This is already known.. I'm talking for this sudden loss of cpu power which seems very weird to me.Any info appreciated.Thanks in advance guys