Sudden FPS slowness

Alright the game I am complaining about is a little off the beatned path...

RealFlight G3.

Hello,

I have been having problems with G3 recently, started about a month ago. I noticed that at times my G3 would lag up, and I was like what the heck is going on, and I checked my FPS, and its way down below what I usually get. I was down to about 55, when I am getting about 150+ on my system. So I turned off shadows and have been flying it like that sense. But I have ran several virus through Trojan hunter, and A squared free. Nothing was pulled up, I then used spybot search and destroy, again nothing of grave danger was pulled up. I have check my graphics card temps, and they are on the high side, @ 90-100* C. But the wierd thing is that sometimes it runs perfectly at the normal fps I have, with shadows on( I notice because I get about 330 fps without shadows.)

I have just also downloaded ATI tool, kicked up the fan to 100% and it had no effect on the game.