Strange framerate problem

Over the last few days I've run into a very strange framerate problem with FSX. I get a slowdown from around 20fps to about 3fps if the following conditions are true:- high resolution display (3840x1024)- VC control panel in view- over a runway at low altitude- flying the Cessna 182, Australian Simulations Warrior, freeware Warrior8 (not checked exhaustively)Changing to any of these closely related conditions do not give a significant slowdown:- lower resolutions (3096x768 or 1280x1024)- over a runway but view direction raised to miss the control panel- adjacent to a runway but with both the VC control panel and the runway in view (i find this very odd!)- flying the DC3, microlight, Goose, or Baron (again I've not checked all the default or other add-on aircraft)This really mucks up the simulator, as I can fly a perfect approach but the instant I pass the runway threshold the framerate slows so much that controlled landing is impossible. It's very annoying that the GA aircraft I want to fly are most affected. Changing between the last few versions of graphics card drivers makes no difference.Has anyone else encountered this sort of thing, and is there a known fix? I suspect that it may have something to do with some of the gauges but have no real way to test this.Running on Athlon64 3800+, Asus A8N-SLI deluxe, 2Gb DDR, dual nVidia 6800GT/SLI, SATA RAID0 array, Soundblaster Live24, Matrox TH2G, 3x19" TFT monitors, Windows x64I hope someone can help!Chris