I started FS9 after FINALLY finishing the backdating process (thanks to Tom Gibson at CalClassic BTW!) and I started a flight. 2 days ago, I could get well into 40 - 60 FPS full overcast with backdated scenery and REX textures and 100% AI. Now, I try a flight on a nice day in KIDL (KJFK) and my FPS is down to 8 in the 2D Cockpit, not to mention the externals as well. I honestly don't know the issue, my system is MORE than capable of FS9 at full settings. Any ideas?

Re-boot your computer and then try.

Wow. What a complex fix! Can't believe that worked, but thanks Jim!