I had been unable to play ANY flight sim for weeks because of a mysterious drop off in frames. I was getting single digits, mayble 2s to 4s sitting on the tarmac. Flying was a practical impossibility. What the problem turned out to be was the presence two evil and particularly sneaky spyware files in the form of trojans. bitDefender missed them, Ad-Aware missed them, and ccleaner failed to clean them. What finally dug them out was Super Anti-Spyware. Immediately afterwards, my frames were back where they were supposed to be. All that being said, what are some common causes of frames suspiciously dropping off? I mean, apart from pixel intense effects and textures? Thanks in advance.