I recently installed the DX10 fixer- and I'm not sure if this is related. I've enjoyed quite excellent performance in FSX in all areas until of late, frames in the mid to high 20s. Lately, I've started flights where the frames are great, then quickly decay to 1-2 FPS, and stay there. I've tried deactivating scenery areas, trying with default aircraft, etc. All have the same result. The funny thing is, it happens mostly over France! Any ideas of what to look for?

I've been able to narrow down the problem to my effects slider- so far if I disable the effects slider in the display preferences, the framerate stays where it should. However, when I bring the slider to the right, the degredation happens quite fast. Starts at 30fps, then degrades down to 2. Funny enough, I'm only getting this in certain geographical areas- and it is mostly over default terrain, not addon scenery.

 

My theory is that something was converted to DX10 by the fixer that wasn't really kosher with my system.

Ok, after replacing my effects folder with the default FSX effects folder (I have a default FSX backup just in case I need to test things), the problem went away. It seems that reconverting the files solved the problem

Try this tool.  You may have to pay for it though:  http://www.thefsps.com/fsx/54-fsps-fsx-fiber-accelerator.html